Anthra[2,3-b:7,6-b&#39;]dithiophene derivatives and their use as organic semiconductors

ABSTRACT

The invention relates to novel anthra[2,3-b:7,6-b′]dithiophene derivatives, methods of their preparation, their use as semiconductors in organic electronic (OE) devices, and to OE devices comprising these derivatives.

FIELD OF THE INVENTION

The invention relates to novel anthra[2,3-b:7,6-b′]dithiophenederivatives, methods of their preparation, their use as semiconductorsin organic electronic (OE) devices, and to OE devices comprising thesederivatives.

BACKGROUND AND PRIOR ART

Linearly fused acenes, like for example pentacene derivatives, are apromising class of molecular semiconducting materials (J. E. Anthony,Angew. Chem. Int. Ed., 2008, 47, 452; J. E. Anthony, Chem. Rev., 2006,106, 5028). When deposited as a thin film by vacuum deposition,pentacene was shown to have hole mobilities in excess of 1 cm² V⁻¹s⁻¹with very high current on/off ratios greater than 10⁶ (S. F. Nelson, Y.Y. Lin, D. J. Gundlach, T. N. Jackson, Appl. Phys. Lett., 1998, 72,1854). However, vacuum deposition is an expensive processing techniquethat is unsuitable for the fabrication of large-area films. Devicefabrication by solution processing was made possible by the introductionof solubilising groups to the pentacene core, namely,trialkylsilylethynyl groups, and yielded mobilities of up to 0.4cm²V⁻¹s⁻¹ (C. D. Sheraw, T. N. Jackson, D. L. Eaton, J. E. Anthony, Adv.Mater., 2003, 15, 2009). Since then, there have been reports of furthersubstitutions of the pentacene core unit to improve its semiconductingperformance in field-effect transistor (FET) devices.

Anthra[2,3-b:7,6-b]dithiophene, which is an iso-electronic structure ofpentacene, has been proved to be another class of molecularsemiconductors with improved performances in field-effect transistors(M. M. Payne, S. R. Parkin, J. E. Anthony, C.-C. Kuo and T. N. Jackson,J. Am. Chem. Soc., 2005, 127 (14), 4986; S. Subramanian, S. K. Park, S.R. Parkin, V. Podzorov, T. N. Jackson, J. E. Anthony, J. Am. Chem. Soc.,2008, 130 (9), 2706) and in organic photovoltaic cells (M. T. Lloyd, A.C. Mayer, S. Subramanian, D. A. Mourey, D. J. Herman, A. V. Bapat, J. E.Anthony, and G. G. Malliaras, J. Am. Chem. Soc., 2007, 129 (29), 9144).Silylethynylated anthra[2,3-b:7,6-b]dithiophenes and their use in OFETand OPV devices are also disclosed in WO 2008/107089 A1 and U.S. Pat.No. 7,385,221 B1.

In order to further improve the carrier mobilities of the acenes, linearelongation by fusing additional aromatic rings have been attempted.However, this approach has been proven to impart instability and reducethe solubility of the materials (M. M. Payne, S. R. Parkin and J. E.Anthony, J. Am. Chem. Soc., 2005, 127(22), 8028. B. Purushothaman, S. R.Parkin and J. E. Anthony, Org. Lett., 2010, 12 (9), 2060).

However, the OSC materials of prior art, and devices comprising them,which have been investigated so far, do still have several drawbacks,and their properties, especially the solubility, processibility,charge-carrier mobility, on/off ratio and stability still leave room forfurther improvement.

Therefore, there is still a need for OSC materials that show goodelectronic properties, especially high charge carrier mobility, and goodprocessibilty, especially a high solubility in organic solvents.Moreover, for use in OFETs there is a need for OSC materials that allowimproved charge injection into the semiconducting layer from thesource-drain electrodes. In addition, for OFETs to be applied in OTFTdriving backplanes for selected display technologies, there is arequirement for the OSC materials to exhibit improved thermal robustnessin order for compatability with annealing processes used inmanufacturing.

It was an aim of the present invention to provide compounds for use asorganic semiconducting materials that do not have the drawbacks of priorart materials as described above, and do especially show goodprocessibility, good solubility in organic solvents, high melting pointsand high charge carrier mobility. Another aim of the invention was toextend the pool of organic semiconducting materials available to theexpert. Other aims of the present invention are immediately evident tothe expert from the following detailed description.

It was found that these aims can be achieved by providing compounds asclaimed in the present invention. In particular, it has been found thatsubstitution of the terminal positions of anthradithiophene withsterically unhindered herteroaryls will lead to co-planar conjugatedstructure, as proved by single crystal X-ray structural analysis. Incontrast to the linearly fusing technique as suggested in prior art,this type of derivatisation does not affect the stability and solubilityof the materials significantly. However, this type of molecules has notbeen reported in the literature so far.

It was also found that OFET devices comprising the new compounds assemiconductors show good mobility and on/off ratio values, and caneasily be prepared using solution deposition fabrication methods andprinting techniques.

SUMMARY OF THE INVENTION

The invention relates to compounds of formula I

wherein

-   one of Y¹ and Y² is —CH═ or ═CH— and the other is —X—,-   one of Y³ and Y⁴ is —CH═ or ═CH— and the other is —X—,-   X is —O—, —S—, —Se— or —NR⁰—,-   R¹ and R² independently of each other denote straight chain,    branched or cyclic alkyl with 1 to 20 C-atoms, which is    unsubstituted or substituted by one or more groups L, and wherein    one or more non-adjacent CH₂ groups are optionally replaced, in each    case independently from one another, by —O—, —S—, —NR⁰—, —SiR⁰R⁰⁰—,    —CY⁰═CY⁰⁰— or —C≡C— in such a manner that O and/or S atoms are not    linked directly to one another, or denote aryl or heteroaryl with 4    to 20 ring atoms which is unsubstituted or substituted by one or    more groups L,-   Ar¹ and Ar² independently of each other denote aryl or heteroaryl    with 4 to 20 ring atoms, which are optionally substituted by one or    more groups L,-   L is selected from P-Sp-, F, Cl, Br, I, —OH, —CN, —NO₂, —NCO, —NCS,    —OCN, —SCN, —C(═O)NR⁰R⁰⁰, —C(═O)X⁰, —C(═O)R⁰, —NR⁰R⁰⁰, C(═O)OH,    optionally substituted silyl or germyl, optionally substituted aryl    or heteroaryl having 4 to 20 ring atoms, straight chain, branched or    cyclic alkyl, alkoxy, oxaalkyl or thioalkyl with 1 to 20, preferably    1 to 12 C atoms which is unsubstituted or substituted with one or    more F or Cl atoms or OH groups, and straight chain, branched or    cyclic alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl,    alkylcarbonyloxy or alkoxycarbonyloxy with 2 to 20, preferably 2 to    12 C atoms which is unsubstituted or substituted with one or more F    or Cl atoms or OH groups,-   P is a polymerisable group,-   Sp is a spacer group or a single bond,-   X⁰ is halogen,-   R⁰ and R⁰⁰ independently of each other denote H or alkyl with 1 to    20 C-atoms,-   Y⁰ and Y⁰⁰ independently of each other denote H, F, Cl or CN,-   m is 1 or 2,-   n is 1 or 2.

The invention further relates to a formulation comprising one or morecompounds of formula I and one or more solvents, preferably selectedfrom organic solvents.

The invention further relates to an organic semiconducting formulationcomprising one or more compounds of formula I, one or more organicbinders, or precursors thereof, preferably having a permittivity E at1,000 Hz of 3.3 or less, and optionally one or more solvents.

The invention further relates to the use of compounds and formulationsaccording to the present invention as charge transport, semiconducting,electrically conducting, photoconducting or light emitting material inan optical, electrooptical, electronic, electroluminescent orphotoluminescent components or devices.

The invention further relates to the use of compounds and formulationsaccording to the present invention as charge transport, semiconducting,electrically conducting, photoconducting or light emitting material inoptical, electrooptical, electronic, electroluminescent orphotoluminescent components or devices.

The invention further relates to a charge transport, semiconducting,electrically conducting, photoconducting or light emitting material orcomponent comprising one or more compounds or formulations according tothe present invention.

The invention further relates to an optical, electrooptical orelectronic component or device comprising one or more compounds,formulations, components or materials according to the presentinvention.

The optical, electrooptical, electronic electroluminescent andphotoluminescent components or devices include, without limitation,organic field effect transistors (OFET), thin film transistors (TFT),integrated circuits (IC), logic circuits, capacitors, radio frequencyidentification (RFID) tags, devices or components, organic lightemitting diodes (OLED), organic light emitting transistors (OLET), flatpanel displays, backlights of displays, organic photovoltaic devices(OPV), solar cells, laser diodes, photoconductors, photodetectors,electrophotographic devices, electrophotographic recording devices,organic memory devices, sensor devices, charge injection layers, chargetransport layers or interlayers in polymer light emitting diodes(PLEDs), organic plasmon-emitting diodes (OPEDs), Schottky diodes,planarising layers, antistatic films, polymer electrolyte membranes(PEM), conducting substrates, conducting patterns, electrode materialsin batteries, alignment layers, biosensors, biochips, security markings,security devices, and components or devices for detecting anddiscriminating DNA sequences.

DETAILED DESCRIPTION OF THE INVENTION

The compounds of the present invention are easy to synthesize andexhibit several advantageous properties, like a high charge carriermobility, a high melting point, a high solubility in organic solvents, agood processability for the device manufacture process, a high oxidativestability and a long lifetime in electronic devices. In addition, theyshow the following advantageous properties:

i) In contrast to the acenes higher than pentacene, the addition ofheteroaryl groups onto the anthradithiophene core is expected to extendthe conjugation length without sacrificing the stability of thematerials. Semi-empirical (PM3) calculations indicate that additionalα-terminal thiophene rings to the ADT core reduce the band gap of themolecule by predominately lowering the LUMO energy level. The HOMOlevel, however, is hardly affected by this type of substitution, asshown in Table 1 below. In this context, the robustness of ADT materialsagainst oxidation will not be affected by this elongation of theπ-system.

TABLE 1

HOMO (eV) LUMO (eV) R = H −7.59 −1.59

−7.60 −1.72

−7.62 −1.80ii) Due to the low single-bond torsional potential in 2,2′-bithiophenes,incorporating five-membered heteroaryls onto the ADT terminals isexpected to create co-planar conjugated molecules in the solid state.The co-planarity has been proven by the single crystal X-ray structuralanalysis of one of the examples of the present invention. The extendedconjugation length of the molecules, combined with solublising groups ofmatching sizes on the perpendicular direction (like R¹ and R² in formulaI), increase the intermolecular π-π overlap by adopting the face-to-facearrangement in the crystalline state and hence enhance the chargemobility by maximizing electronic coupling between adjacent molecules.iii) The low single-bond torsional potential in 2,2′-bithiophenes asdescribed above enables essential free-rotation of the terminalheteroaryl groups in the solution states. Thus, these new molecules willbe expected to have higher solubilities compared with the fused ringanalogues of similar lengths. Good solubility of organic semi-conductingmaterials is of crucial importance to solution processing viamass-production printing techniques such as ink-jet printing. Some ofthe examples of this invention possess solubilities >1 wt. % inhalogenated hydrocarbons, alkylated benzenes, THF and oligo(ethyleneglycol) dialkyl ethers.iv) An additional benefit gained by the enhanced conjugation length ofthe new molecules is that the melting temperature increases. This is adirect result of the increased intermolecular π-π interactions, henceincreased lattice energy in the crystalline states of conjugatedmolecules. Differential scanning calorimetry measurements show that mostof the crystalline solids in this invention do not melt under 300° C.Morphological stability of the thin crystalline films of semiconductingmaterials is essential when any annealing process is required duringdevice production, and when localised spot temperatures may rise inworking devices.

Preferably in the compounds of formula I X in each occurrence in thegroups Y¹⁻⁴ has the same meaning.

Very preferred are compounds of formula I wherein X is S.

Further preferred are compounds of formula I wherein n and m have thesame meaning.

Further preferred are compounds of formula I wherein n=m=1.

The heteroacenes of the present invention are usually prepared as amixture of isomers. Formula I thus covers isomer pairs wherein in thefirst isomer Y¹=Y³ and Y²=Y⁴, and in the second isomer Y¹=Y⁴ and Y²=Y³.

The compounds of the present invention include both the mixture of theseisomers and the pure isomers.

The pure isomers may be obtained from the mixture of isomers for exampleby methods known to those skilled in the art, including but not limitedto high-performance liquid chromatography (HPLC).

R¹ and R² in formula I are preferably identical groups.

Very preferred are compounds of formula I wherein R¹ and/or R² denote—C≡C—R³, wherein R³ is an optionally substituted silyl or germyl group,or an aryl or heteroaryl group with 1 to 20 ring atoms which isunsubstituted or substituted by one or more groups L as defined above.

If R³ or L is an optionally substituted silyl or germyl group, it ispreferably selected of the formula II-AR′R″R′″  IIwherein

-   A is Si or Ge, preferably Si, and-   R′, R″, R′″ are identical or different groups selected from the    group consisting of H, a straight-chain, branched or cyclic alkyl or    alkoxy group having 1 to 20 C atoms, a straight-chain, branched or    cyclic alkenyl group having 2 to 20 C atoms, a straight-chain,    branched or cyclic alkynyl group having 2 to 20 C atoms, a    straight-chain, branched or cyclic alkylcarbonyl group having 2 to    20 C atoms, an aryl or heteroaryl group having 4 to 20 ring atoms,    an arylalkyl or heteroarylalkyl group having 4 to 20 ring atoms, an    aryloxy or heteroaryloxy group having 4 to 20 ring atoms, or an    arylalkyloxy or heteroarylalkyloxy group having 4 to 20 ring atoms,    wherein all the aforementioned groups are optionally substituted    with one or more groups L′, and-   L′ has one of the meanings given for L in formula I, which is    different from a silyl and germyl group.

Preferably, R′, R″ and R′″ are each independently selected fromoptionally substituted and straight-chain, branched or cyclic alkyl oralkoxy having 1 to 10 C atoms, which is for example methyl, ethyl,n-propyl, isopropyl, cyclopropyl, 2,3-dimethylcyclopropyl,2,2,3,3-tetramethylcyclopropyl, cyclobutyl, cyclopentyl, methoxy orethoxy, optionally substituted and straight-chain, branched or cyclicalkenyl, alkynyl or alkylcarbonyl having 2 to 12 C atoms, which is forexample allyl, isopropenyl, 2-but-1-enyl, cis-2-but-2-enyl,3-but-1-enyl, propynyl or acetyl, optionally substituted aryl,heteroaryl, arylalkyl or heteroarylalkyl, aryloxy or heteroaryloxyhaving 5 to 10 ring atoms, which is for example phenyl, p-tolyl, benzyl,2-furanyl, 2-thienyl, 2-selenophenyl, N-methylpyrrol-2-yl or phenoxy.

Further preferred is a silyl or germyl group of formula II wherein oneor more of R′, R″ and R′″ together with the Si or Ge atom form a cyclicgroup, preferably having 2 to 8 C atoms.

Preferably Ar¹ and/or Ar² in formula I denote an aromatic orheteroaromatic group with 4 to 25 ring atoms, which is mono- orpolycyclic, i.e. it may also contain two or more individual rings thatare connected to each other via single bonds, or contain two or morefused rings, and wherein each ring is unsubstituted or substituted withone or more groups L as defined above.

Very preferably Ar¹ and/or Ar² in formula I are selected from the groupconsisting of furan, thiophene, selenophene, N-pyrrole, pyrimidine,thiazole, thiadiazole, oxazole, oxadiazole, selenazole, and bi-, tri- ortetracyclic groups containing one or more of the aforementioned ringsand optionally one or more benzene rings, wherein the individual ringsare connected by single bonds or fused with each other, and wherein allthe aforementioned groups are unsubstituted, or substituted with one ormore groups L as defined above.

Preferred aryl or heteraryl groups containing fused rings are forexample thieno[3,2-b]thiophene, dithieno[3,2-b:2′,3′-d]thiophene,selenopheno[3,2-b]selenophene-2,5-diyl,selenopheno[2,3-b]selenophene-2,5-diyl,selenopheno[3,2-b]thiophene-2,5-diyl,selenopheno[2,3-b]thiophene-2,5-diyl,benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl, 2,2-dithiophene,2,2-diselenophene, dithieno[3,2-b:2′,3′-d]silole-5,5-diyl,4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl, benzo[b]thiophene,benzo[b]selenophene, benzooxazole, benzothiazole, benzoselenazole,wherein all the aforementioned groups are unsubstituted, or substitutedwith one or more groups L as defined above.

Most preferably Ar¹ and/or Ar² in formula I are selected from the groupconsisting of the following moieties:

wherein X has one of the meanings of L given above, and is preferably H,F, Cl, Br, I, CN, COOH, COOR⁰, CONR⁰R⁰⁰, or alkyl or perfluoroalkylhaving 1 to 20 C atoms, o is 1, 2, 3 or 4, and the dashed line denotesthe linkage to the adjacent ring in formula I.

Very preferred compounds of formula I are those of the followingformulae:

wherein R′, R″ and R′″ are as defined in formula II.

Above and below, an alkyl group or an alkoxy group, i.e. alkyl where theterminal CH₂ group is replaced by —O—, can be straight-chain orbranched. It is preferably straight-chain, has 2, 3, 4, 5, 6, 7 or 8carbon atoms and accordingly is preferably ethyl, propyl, butyl, pentyl,hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy,or octoxy, furthermore methyl, nonyl, decyl, undecyl, dodecyl, tridecyl,tetradecyl, pentadecyl, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy ortetradecoxy, for example.

An alkenyl group, i.e. alkyl wherein one or more CH₂ groups are replacedby —CH═CH— can be straight-chain or branched. It is preferablystraight-chain, has 2 to 10 C atoms and accordingly is preferably vinyl,prop-1-, or prop-2-enyl, but-1-, 2- or but-3-enyl, pent-1-, 2-, 3- orpent-4-enyl, hex-1-, 2-, 3-, 4- or hex-5-enyl, hept-1-, 2-, 3-, 4-, 5-or hept-6-enyl, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-,3-, 4-, 5-, 6-, 7- or non-8-enyl, dec-1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- ordec-9-enyl.

Especially preferred alkenyl groups are C₂-C₇-1E-alkenyl,C₄-C₇-3E-alkenyl, C₅-C₇-4-alkenyl, C₆-C₇-5-alkenyl and C₇-6-alkenyl, inparticular C₂-C₇-1E-alkenyl, C₄-C₇-3E-alkenyl and C₅-C₇-4-alkenyl.Examples for particularly preferred alkenyl groups are vinyl,1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl,3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl,4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groupshaving up to 5 C atoms are generally preferred.

An oxaalkyl group, i.e. alkyl where a non-terminal CH₂ group is replacedby —O—, is preferably straight-chain 2-oxapropyl (=methoxymethyl), 2-,(=ethoxymethyl) or 3-oxabutyl (=2-methoxyethyl), 2-, 3-, or 4-oxapentyl,2-, 3-, 4-, or 5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-,5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-,4-, 5-, 6-, 7-, 8- or 9-oxadecyl, for example.

In an alkyl group wherein one CH₂ group is replaced by —O— and anotherCH₂ group is replaced by —CO—, these radicals are preferablyneighboured. Accordingly these radicals together form a carbonyloxygroup —CO—O— or an oxycarbonyl group —O—CO—. Preferably this group isstraight-chain and has 2 to 6 C atoms. It is accordingly preferablyacetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy,acetyloxymethyl, propionyloxy-methyl, butyryloxymethyl,pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxyethyl,2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyl-oxypropyl,4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl,butoxycarbonyl, pentoxycarbonyl, methoxycarbonyl-methyl,ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonyl-methyl,2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl,2-(propoxy-carbonyl)ethyl, 3-(methoxycarbonyl)propyl,3-(ethoxycarbonyl)propyl, 4-(methoxycarbonyl)-butyl.

An alkyl group wherein two or more CH₂ groups are replaced by —O— and/or—COO— can be straight-chain or branched. It is preferably straight-chainand has 3 to 12 C atoms. Accordingly it is preferablybis-carboxy-methyl, 2,2-bis-carboxy-ethyl, 3,3-bis-carboxy-propyl,4,4-bis-carboxy-butyl, 5,5-bis-carboxy-pentyl, 6,6-bis-carboxy-hexyl,7,7-bis-carboxy-heptyl, 8,8-bis-carboxy-octyl, 9,9-bis-carboxy-nonyl,10,10-bis-carboxy-decyl, bis-(methoxycarbonyl)-methyl,2,2-bis-(methoxycarbonyl)-ethyl, 3,3-bis-(methoxycarbonyl)-propyl,4,4-bis-(methoxycarbonyl)-butyl, 5,5-bis-(methoxycarbonyl)-pentyl,6,6-bis-(methoxycarbonyl)-hexyl, 7,7-bis-(methoxycarbonyl)-heptyl,8,8-bis-(methoxycarbonyl)-octyl, bis-(ethoxycarbonyl)-methyl,2,2-bis-(ethoxycarbonyl)-ethyl, 3,3-bis-(ethoxycarbonyl)-propyl,4,4-bis-(ethoxycarbonyl)-butyl, 5,5-bis-(ethoxycarbonyl)-hexyl.

A thioalkyl group, i.e. where one CH₂ group is replaced by —S—, ispreferably straight-chain thiomethyl (—SCH₃), 1-thioethyl (—SCH₂CH₃),1-thiopropyl (=—SCH₂CH₂CH₃), 1-(thiobutyl), 1-(thiopentyl),1-(thiohexyl), 1-(thioheptyl), 1-(thiooctyl), 1-(thiononyl),1-(thiodecyl), 1-(thioundecyl) or 1-(thiododecyl), wherein preferablythe CH₂ group adjacent to the sp² hybridised vinyl carbon atom isreplaced.

R¹, R², R′, R″ and R′″ can be an achiral or a chiral group. Particularlypreferred chiral groups are 2-butyl (=1-methylpropyl), 2-methylbutyl,2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, inparticular 2-methylbutyl, 2-methylbutoxy, 2-methylpentoxy,3-methylpentoxy, 2-ethyl-hexoxy, 1-methylhexoxy, 2-octyloxy,2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl, 2-hexyl,2-octyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methoxyoctoxy, 6-methyloctoxy,6-methyloctanoyloxy, 5-methylheptyl-oxycarbonyl, 2-methylbutyryloxy,3-methylvaleroyloxy, 4-methylhexanoy-loxy, 2-chlorpropionyloxy,2-chloro-3-methylbutyryloxy, 2-chloro-4-methylvaleryloxy,2-chloro-3-methylvaleryloxy, 2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl,1-methoxypropyl-2-oxy, 1-ethoxypropyl-2-oxy, 1-propoxypropyl-2-oxy,1-butoxypropyl-2-oxy, 2-fluorooctyloxy, 2-fluorodecyloxy,1,1,1-trifluoro-2-octyloxy, 1,1,1-trifluoro-2-octyl,2-fluoromethyloctyloxy for example. Very preferred are 2-hexyl, 2-octyl,2-octyloxy, 1,1,1-trifluoro-2-hexyl, 1,1,1-trifluoro-2-octyl and1,1,1-trifluoro-2-octyloxy.

Preferred achiral branched groups are isopropyl, isobutyl(=methylpropyl), isopentyl (=3-methylbutyl), tertiary butyl, isopropoxy,2-methylpropoxy and 3-methylbutoxy.

—CY⁰═CY⁰⁰— is preferably —CH═CH—, —CF═CF— or —CH═C(CN)—.

Halogen is F, Cl, Br or I, preferably F, Cl or Br.

The compounds of formula I may also be substituted with a polymerisableor reactive group, which is optionally protected during the process offorming the polymer. Particular preferred compounds of this type arethose of formula I that contain one or more substituents L which denoteP-Sp, wherein P is a polymerisable or reactive group and Sp is a spacergroup or a single bond. These compounds are particularly useful assemiconductors or charge transport materials, as they can be crosslinkedvia the groups P, for example by polymerisation in situ, during or afterprocessing the polymer into a thin film for a semiconductor component,to yield crosslinked polymer films with high charge carrier mobility andhigh thermal, mechanical and chemical stability.

Preferably the polymerisable or reactive group P is selected fromCH₂═CW¹—COO—, CH₂═CW¹—CO—

CH₂═CW²—(O)_(k1)—, CH₃—CH═CH—O—, (CH₂═CH)₂CH—OCO—, (CH₂═CH—CH₂)₂CH—OCO—,(CH₂═CH)₂CH—O—, (CH₂═CH—CH₂)₂N—, (CH₂═CH—CH₂)₂N—CO—, HO—CW²W³—,HS—CW²W³—, HW²N—, HO—CW²W³—NH—, CH₂═CW¹—CO—NH—,CH₂═CH—(COO)_(k1)-Phe-(O)_(k2)—, CH₂═CH—(CO)_(k1)-Phe-(O)_(k2)—,Phe-CH═CH—, HOOC—, OCN—, and W⁴W⁵W⁶Si—, with W¹ being H, F, Cl, CN, CF₃,phenyl or alkyl with 1 to 5 C-atoms, in particular H, Cl or CH₃, W² andW³ being independently of each other H or alkyl with 1 to 5 C-atoms, inparticular H, methyl, ethyl or n-propyl, W⁴, W⁵ and W⁶ beingindependently of each other Cl, oxaalkyl or oxacarbonylalkyl with 1 to 5C-atoms, W⁷ and W⁸ being independently of each other H, Cl or alkyl with1 to 5 C-atoms, Phe being 1,4-phenylene that is optionally substitutedby one or more groups L as defined above, and k₁ and k₂ beingindependently of each other 0 or 1.

Alternatively P is a protected derivative of these groups which isnon-reactive under the conditions described for the process according tothe present invention. Suitable protective groups are known to theordinary expert and described in the literature, for example in Green,“Protective Groups in Organic Synthesis”, John Wiley and Sons, New York(1981), like for example acetals or ketals.

Especially preferred groups P are CH₂═CH—COO—, CH₂═C(CH₃)—COO—, CH₂═CH—,CH₂═CH—O—, (CH₂═CH)₂CH—OCO—, (CH₂═CH)₂CH—O—,

or protected derivatives thereof.

Polymerisation of group P can be carried out according to methods thatare known to the ordinary expert and described in the literature, forexample in D. J. Broer; G. Challa; G. N. Mol, Macromol. Chem., 1991,192, 59.

The term “spacer group” is known in prior art and suitable spacer groupsSp are known to the ordinary expert (see e.g. Pure Appl. Chem. 2001,73(5), 888. The spacer group Sp is preferably of formula Sp′-X′, suchthat P-Sp- is P-Sp′-X′—, wherein

-   Sp′ is alkylene with up to 30 C atoms which is unsubstituted or    mono- or polysubstituted by F, Cl, Br, I or CN, it being also    possible for one or more non-adjacent CH₂ groups to be replaced, in    each case independently from one another, by —O—, —S—, —NH—, —NR⁰—,    —SiR⁰R⁰⁰—, —CO—, —COO—, —COO—, —COO—O—, —S—CO—, —CO—S—, —CH═CH— or    —C≡C— in such a manner that O and/or S atoms are not linked directly    to one another,-   X′ is —O—, —S—, —CO—, —COO—, —COO—, —O—COO—, —CO—NR⁰—, —NR⁰—CO—,    —NR⁰—CO—NR⁰⁰—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—, —OCF₂—,    —CF₂S—, —SCF₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—, —CH═N—, —N═CH—, —N═N—,    —CH═CR⁰—, —CY⁰═CY⁰⁰—, —C≡C—, —CH═CH—COO—, —OCO—CH═CH— or a single    bond,-   R⁰ and R⁰⁰ are independently of each other H or alkyl with 1 to 12    C-atoms, and-   Y⁰ and Y⁰⁰ are independently of each other H, F, Cl or CN.-   X′ is preferably —O—, —S—, —OCH₂—, —CH₂O—, —SCH₂—, —CH₂S—, —CF₂O—,    —OCF₂—, —CF₂S—, —SCF₂—, —CH₂CH₂—, —CF₂CH₂—, —CH₂CF₂—, —CF₂CF₂—,    —CH═N—, —N═CH—, —N═N—, —CH═CR⁰—, —CY⁰═CY⁰⁰—, —C≡C— or a single bond,    in particular —O—, —S—, —C≡C—, —CY⁰═CY⁰⁰— or a single bond. In    another preferred embodiment X′ is a group that is able to form a    conjugated system, such as —C≡C— or —CY⁰═CY⁰⁰—, or a single bond.

Typical groups Sp′ are, for example, —(CH₂)_(p)—,—(CH₂CH₂O)_(q)—CH₂CH₂—, —CH₂CH₂—S—CH₂CH₂— or —CH₂CH₂—NH—CH₂CH₂— or—(SiR⁰R⁰⁰—O)_(p)—, with p being an integer from 2 to 12, q being aninteger from 1 to 3 and R⁰ and R⁰⁰ having the meanings given above.

Preferred groups Sp′ are ethylene, propylene, butylene, pentylene,hexylene, heptylene, octylene, nonylene, decylene, undecylene,dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene,ethylene-thioethylene, ethylene-N-methyl-iminoethylene,1-methylalkylene, ethenylene, propenylene and butenylene for example.

The compounds of formula I can be synthesized according to or in analogyto methods that are known to the skilled person and are described in theliterature. Other methods of preparation can be taken from the examples.Especially preferred and suitable synthesis methods are furtherdescribed below.

A suitable and preferred synthesis of terminal dithienylanthra[2,3-b:7,6-b]dithiophenes with added trialkylsilylethynylsolubilising groups is exemplarily and schematically shown in Schemes 1and 2 below. Other heteroaryl derivatives can be synthesised inanalogous manner.

As shown in Scheme 1, commercially available diacetal A is iodinated bytreating with n-BuLi and elemental iodine to yield the iododiacetal B ingood yield. The diacetal is deprotected to the corresponding thedialdehyde C, which is condensed with 1,4-cyclohexanedione to yield thediiodoanthradithiophene quinone D. The quinone reacts with lithiumtrialkysilylacetylide to form the dihydroxy derivative E. Stille orSuzuki coupling of E with the corresponding thienyl building blocksyields F, which aromatises to the dithienylanthra[2,3-b:7,6-b]dithiophenes.

The fluorinated dithienyl anthra[2,3-b:7,6-b]dithiophenes can besynthesised by analogous methods as shown in Scheme 2.

The novel methods of preparing compounds as described above and beloware another aspect of the invention. Very preferred is a method ofpreparing a compound of formula I comprising the following steps:

-   a) 2,3-Thiophenedicarboxaldehyde diacetal (A) is halogenated by    lithiation with alkyllithium, LDA or another lithiation reagent, and    then reacted with a halogenation agent including but not limited to    N-chlorosuccinimide, carbon tetrachloride, N-bromosuccinimide,    carbon tetrabromide, N-iodosuccinimide, iodinechloride, elemental    iodine, to afford the 5-halogenated 2,3-thiophenedicarboxaldehyde    diacetal (B).-   b) The 5-halogenated 2,3-thiophenedicarboxaldehyde diacetal (B) is    deprotected under acidic conditions to the corresponding dialdehyde    (C), which is then condensed with a cyclic 1,4-diketone, such as    1,4-cyclohexadione, 1,4-dihydroxy-naphthalene or its higher    analogues, to yield the quinone of the dihalogenated    acenodithiophene (D).-   c) The quinone of the dihalogenated acenodithiophene (D) is treated    with silylethynyllithium, followed by a hydrolysis, for example with    diluted HCl, to yield the dihalogenated diol intermediate (E).-   d) Heteroaryl groups are introduced in the dihalogenated diol    intermediate (E) by cross-coupling it with a corresponding    heteroaryl boronic acid, boronic ester, stannane, zink halide or    magnesium halide, in the presence of a nickel or palladium complex    as catalyst, to yield the heteroaryl extended diol (F).-   e) The heteroaryl extended diol (F) is aromatised using a reducing    agent under acidic conditions to afford the terminally substituted    heteroaryl acenodithiophene (1,2).-   f) Alternatively to steps b)-e), the 5-halogenated    2,3-thiophenedicarbox-aldehyde diacetal (B) obtained by step a) is    reacted in a cross-coupling reaction with a corresponding heteroaryl    boronic acid, boronic ester, stannane, zink halide or magnesium    halide, in the presence of a nickel or palladium complex as    catalyst. The resulting product is deprotected and condensed with a    cyclic 1,4-diketone as described in step b), followed by treatment    with silylethynyllithium and hydrolysis as described in step c), and    the resulting heteroaryl extended diol is aromatised as described in    step e).

The invention further relates to a formulation comprising one or morecompounds of formula I and one or more solvents, preferably selectedfrom organic solvents.

Preferred solvents are aliphatic hydrocarbons, chlorinated hydrocarbons,aromatic hydrocarbons, ketones, ethers and mixtures thereof. Additionalsolvents which can be used include 1,2,4-trimethylbenzene,1,2,3,4-tetramethyl benzene, pentylbenzene, mesitylene, cumene, cymene,cyclohexylbenzene, diethylbenzene, tetralin, decalin, 2,6-lutidine,2-fluoro-m-xylene, 3-fluoro-o-xylene, 2-chlorobenzotrifluoride,dimethylformamide, 2-chloro-6-fluorotoluene, 2-fluoroanisole, anisole,2,3-dimethylpyrazine, 4-fluoroanisole, 3-fluoroanisole,3-trifluoro-methylanisole, 2-methylanisole, phenetol, 4-methylansiole,3-methylanisole, 4-fluoro-3-methylanisole, 2-fluorobenzonitrile,4-fluoroveratrol, 2,6-dimethylanisole, 3-fluorobenzonitrile,2,5-dimethylanisole, 2,4-dimethylanisole, benzonitrile,3,5-dimethylanisole, N,N-dimethylaniline, ethyl benzoate,1-fluoro-3,5-dimethoxybenzene, 1-methylnaphthalene,N-methylpyrrolidinone, 3-fluorobenzotrifluoride, benzotrifluoride,benzotrifluoride, diosane, trifluoromethoxybenzene,4-fluorobenzotrifluoride, 3-fluoropyridine, toluene, 2-fluorotoluene,2-fluorobenzotrifluoride, 3-fluorotoluene, 4-isopropylbiphenyl, phenylether, pyridine, 4-fluorotoluene, 2,5-difluorotoluene,1-chloro-2,4-difluorobenzene, 2-fluoropyridine, 3-chlorofluorobenzene,3-chlorofluorobenzene, 1-chloro-2,5-difluorobenzene,4-chlorofluorobenzene, chlorobenzene, o-dichlorobenzene,2-chlorofluorobenzene, p-xylene, m-xylene, o-xylene or mixture of o-,m-, and p-isomers. Solvents with relatively low polarity are generallypreferred. For inkjet printing solvents with high boiling temperaturesand solvent mixtures are preferred. For spin coating alkylated benzeneslike xylene and toluene are preferred.

The invention further relates to an organic semiconducting formulationcomprising one or more compounds of formula I, one or more organicbinders, or precursors thereof, preferably having a permittivity E at1,000 Hz of 3.3 or less, and optionally one or more solvents.

Combining specified soluble compounds of formula I, especially compoundsof the preferred formulae as described above and below, with an organicbinder resin (hereinafter also referred to as “the binder”) results inlittle or no reduction in charge mobility of the compounds of formula I,even an increase in some instances. For instance, the compounds offormula I may be dissolved in a binder resin (for examplepoly(α-methylstyrene) and deposited (for example by spin coating), toform an organic semiconducting layer yielding a high charge mobility.Moreover, a semiconducting layer formed thereby exhibits excellent filmforming characteristics and is particularly stable.

If an organic semiconducting layer formulation of high mobility isobtained by combining a compound of formula I with a binder, theresulting formulation leads to several advantages. For example, sincethe compounds of formula I are soluble they may be deposited in a liquidform, for example from solution. With the additional use of the binderthe formulation can be coated onto a large area in a highly uniformmanner. Furthermore, when a binder is used in the formulation it ispossible to control the properties of the formulation to adjust toprinting processes, for example viscosity, solid content, surfacetension. Whilst not wishing to be bound by any particular theory it isalso anticipated that the use of a binder in the formulation fills involume between crystalline grains otherwise being void, making theorganic semiconducting layer less sensitive to air and moisture. Forexample, layers formed according to the process of the present inventionshow very good stability in OFET devices in air.

The invention also provides an organic semiconducting layer whichcomprises the organic semiconducting layer formulation.

The invention further provides a process for preparing an organicsemiconducting layer, said process comprising the following steps:

-   (i) depositing on a substrate a liquid layer of a formulation    comprising one or more compounds of formula I as described above and    below, one or more organic binder resins or precursors thereof, and    optionally one or more solvents,-   (ii) forming from the liquid layer a solid layer which is the    organic semiconducting layer,-   (iii) optionally removing the layer from the substrate.

The process is described in more detail below.

The invention additionally provides an electronic device comprising thesaid organic semiconducting layer. The electronic device may include,without limitation, an organic field effect transistor (OFET), organiclight emitting diode (OLED), photodetector, sensor, logic circuit,memory element, capacitor or photovoltaic (PV) cell. For example, theactive semiconductor channel between the drain and source in an OFET maycomprise the layer of the invention. As another example, a charge (holeor electron) injection or transport layer in an OLED device may comprisethe layer of the invention. The formulations according to the presentinvention and layers formed therefrom have particular utility in OFETsespecially in relation to the preferred embodiments described herein.

The semiconducting compound of formula I preferably has a charge carriermobility, μ, of more than 0.001 cm²V⁻¹s⁻¹, very preferably of more than0.01 cm²V⁻¹s⁻¹, especially preferably of more than 0.1 cm²V⁻¹s⁻¹ andmost preferably of more than 0.5 cm²V⁻¹s⁻¹.

The binder, which is typically a polymer, may comprise either aninsulating binder or a semiconducting binder, or mixtures thereof may bereferred to herein as the organic binder, the polymeric binder or simplythe binder.

Preferred binders according to the present invention are materials oflow permittivity, that is, those having a permittivity E at 1,000 Hz of3.3 or less. The organic binder preferably has a permittivity E at 1,000Hz of 3.0 or less, more preferably 2.9 or less. Preferably the organicbinder has a permittivity E at 1,000 Hz of 1.7 or more. It is especiallypreferred that the permittivity of the binder is in the range from 2.0to 2.9. Whilst not wishing to be bound by any particular theory it isbelieved that the use of binders with a permittivity E of greater than3.3 at 1,000 Hz, may lead to a reduction in the OSC layer mobility in anelectronic device, for example an OFET. In addition, high permittivitybinders could also result in increased current hysteresis of the device,which is undesirable.

An example of a suitable organic binder is polystyrene. Further examplesof suitable binders are disclosed for example in US 2007/0102696 A1.Especially suitable and preferred binders are described in thefollowing.

In one type of preferred embodiment, the organic binder is one in whichat least 95%, more preferably at least 98% and especially all of theatoms consist of hydrogen, fluorine and carbon atoms.

It is preferred that the binder normally contains conjugated bonds,especially conjugated double bonds and/or aromatic rings.

The binder should preferably be capable of forming a film, morepreferably a flexible film. Polymers of styrene and α-methyl styrene,for example copolymers including styrene, α-methylstyrene and butadienemay suitably be used.

Binders of low permittivity of use in the present invention have fewpermanent dipoles which could otherwise lead to random fluctuations inmolecular site energies. The permittivity c (dielectric constant) can bedetermined by the ASTM D150 test method.

It is also preferred that in the present invention binders are usedwhich have solubility parameters with low polar and hydrogen bondingcontributions as materials of this type have low permanent dipoles. Apreferred range for the solubility parameters (‘Hansen parameter’) of abinder for use in accordance with the present invention is provided inTable 1 below.

TABLE 1 Hansen parameter δ_(d) MPa^(1/2) δ_(p) MPa^(1/2) δ_(h) MPa^(1/2)Preferred range   14.5+  0-10 0-14 More preferred range 16+ 0-9 0-12Most preferred range 17+ 0-8 0-10

The three dimensional solubility parameters listed above include:dispersive (δ_(d)), polar (δ_(p)) and hydrogen bonding (δ_(h))components (C. M. Hansen, Ind. Eng. and Chem., Prod. Res. and Devl., 9,No 3, p 282., 1970). These parameters may be determined empirically orcalculated from known molar group contributions as described in Handbookof Solubility Parameters and Other Cohesion Parameters ed. A. F. M.Barton, CRC Press, 1991. The solubility parameters of many knownpolymers are also listed in this publication.

It is desirable that the permittivity of the binder has littledependence on frequency. This is typical of non-polar materials.Polymers and/or copolymers can be chosen as the binder by thepermittivity of their substituent groups. A list of suitable andpreferred low polarity binders is given (without limiting to theseexamples) in Table 2:

TABLE 2 typical low frequency Binder permittivity (ε) polystyrene 2.5poly(α-methylstyrene) 2.6 poly(α-vinylnaphtalene) 2.6 poly(vinyltoluene)2.6 polyethylene 2.2-2.3 cis-polybutadiene 2.0 polypropylene 2.2poly(4-methyl-1-pentene) 2.1 poly (4-methylstyrene) 2.7poly(chorotrifluoroethylene) 2.3-2.8 poly(2-methyl-1,3-butadiene) 2.4poly(p-xylylene) 2.6 poly(α-α-α′-α′ tetrafluoro-p-xylylene) 2.4poly[1,1-(2-methyl propane)bis(4-phenyl)carbonate] 2.3 poly(cyclohexylmethacrylate) 2.5 poly(chlorostyrene) 2.6poly(2,6-dimethyl-1,4-phenylene ether) 2.6 polyisobutylene 2.2poly(vinyl cyclohexane) 2.2 poly(vinylcinnamate) 2.9poly(4-vinylbiphenyl) 2.7

Further preferred binders are poly(1,3-butadiene) and polyphenylene.

Especially preferred are formulations wherein the binder is selectedfrom poly-α-methyl styrene, polystyrene and polytriarylamine or anycopolymers of these, and the solvent is selected from xylene(s),toluene, tetralin and cyclohexanone.

Copolymers containing the repeat units of the above polymers are alsosuitable as binders. Copolymers offer the possibility of improvingcompatibility with the compounds of formula I, modifying the morphologyand/or the glass transition temperature of the final layer composition.It will be appreciated that in the above table certain materials areinsoluble in commonly used solvents for preparing the layer. In thesecases analogues can be used as copolymers. Some examples of copolymersare given in Table 3 (without limiting to these examples). Both randomor block copolymers can be used. It is also possible to add more polarmonomer components as long as the overall composition remains low inpolarity.

TABLE 3 typical low frequency Binder permittivity (ε)poly(ethylene/tetrafluoroethylene) 2.6poly(ethylene/chlorotrifluoroethylene) 2.3 fluorinatedethylene/propylene copolymer   2-2.5 polystyrene-co-α-methylstyrene2.5-2.6 ethylene/ethyl acrylate copolymer 2.8 poly(styrene/10%butadiene) 2.6 poly(styrene/15% butadiene) 2.6 poly(styrene/2,4dimethylstyrene) 2.5 Topas ™ (all grades) 2.2-2.3

Other copolymers may include: branched or non-branchedpolystyrene-block-polybutadiene,polystyrene-block(polyethylene-ran-butylene)-block-polystyrene,polystyrene-block-polybutadiene-block-polystyrene,polystyrene-(ethylene-propylene)-diblock-copolymers (e.g.KRATON®-G1701E, Shell), poly(propylene-co-ethylene) andpoly(styrene-co-methylmethacrylate).

Preferred insulating binders for use in the organic semiconductor layerformulation according to the present invention arepoly(α-methylstyrene), polyvinylcinnamate, poly(4-vinylbiphenyl),poly(4-methylstyrene), and Topas™ 8007 (linear olefin,cyclo-olefin(norbornene) copolymer available from Ticona, Germany). Mostpreferred insulating binders are poly(α-methylstyrene),polyvinylcinnamate and poly(4-vinylbiphenyl).

The binder can also be selected from crosslinkable binders, like e.g.acrylates, epoxies, vinylethers, thiolenes etc., preferably having asufficiently low permittivity, very preferably of 3.3 or less. Thebinder can also be mesogenic or liquid crystalline.

As mentioned above the organic binder may itself be a semiconductor, inwhich case it will be referred to herein as a semiconducting binder. Thesemiconducting binder is still preferably a binder of low permittivityas herein defined. Semiconducting binders for use in the presentinvention preferably have a number average molecular weight (M_(n)) ofat least 1500-2000, more preferably at least 3000, even more preferablyat least 4000 and most preferably at least 5000. The semiconductingbinder preferably has a charge carrier mobility, μ, of at least 10⁻⁵cm²V⁻¹s⁻¹, more preferably at least 10⁻⁴ cm²V⁻¹s⁻¹.

A preferred class of semiconducting binder is a polymer as disclosed inU.S. Pat. No. 6,630,566, preferably an oligomer or polymer having repeatunits of formula 1:

wherein

-   Ar¹¹, Ar²² and Ar³³ which may be the same or different, denote,    independently if in different repeat units, an optionally    substituted aromatic group that is mononuclear or polynuclear, and-   m is an integer ≧1, preferably ≧6, preferably ≧10, more preferably    ≧15 and most preferably ≧20.

In the context of Ar¹¹, Ar²² and Ar³³, a mononuclear aromatic group hasonly one aromatic ring, for example phenyl or phenylene. A polynucleararomatic group has two or more aromatic rings which may be fused (forexample napthyl or naphthylene), individually covalently linked (forexample biphenyl) and/or a combination of both fused and individuallylinked aromatic rings. Preferably each Ar¹¹, Ar²² and Ar³³ is anaromatic group which is substantially conjugated over substantially thewhole group.

Further preferred classes of semiconducting binders are those containingsubstantially conjugated repeat units. The semiconducting binder polymermay be a homopolymer or copolymer (including a block-copolymer) of thegeneral formula 2:A_((c))B_((d)) . . . Z_((z))  2

wherein A, B, . . . , Z each represent a monomer unit and (c), (d), . .. (z) each represent the mole fraction of the respective monomer unit inthe polymer, that is each (c), (d), . . . (z) is a value from 0 to 1 andthe total of (c)+(d)+ . . . +(z)=1.

Examples of suitable and preferred monomer units A, B, . . . Z includeunits of formula 1 above and of formulae 3 to 8 given below (wherein mis as defined in formula 1:

wherein

-   R^(a) and R^(b) are independently of each other selected from H, F,    CN, NO₂, —N(R^(c))(R^(d)) or optionally substituted alkyl, alkoxy,    thioalkyl, acyl, aryl,-   R^(c) and R^(d) are independently or each other selected from H,    optionally substituted alkyl, aryl, alkoxy or polyalkoxy or other    substituents,    and wherein the asterisk (*) is any terminal or end capping group    including H, and the alkyl and aryl groups are optionally    fluorinated;

wherein

-   Y is Se, Te, O, S or —N(R^(e)), preferably O, S or —N(R^(e))—,-   R^(e) is H, optionally substituted alkyl or aryl,-   R^(a) and R^(b) are as defined in formula 3;

wherein R^(a), R^(b) and Y are as defined in formulae 3 and 4;

wherein R^(a), R^(b) and Y are as defined in formulae 3 and 4,

-   Z is —C(T¹)=C(T²)-, —C≡C—, —N(R^(f))—, —N═N—, (R^(f))═N—,    —N═C(R^(f))—,-   T¹ and T² independently of each other denote H, Cl, F, —CN or lower    alkyl with 1 to 8 C atoms,-   R^(f) is H or optionally substituted alkyl or aryl;

wherein R^(a) and R^(b) are as defined in formula 3;

wherein R^(a), R^(b), R^(g) and R^(h) independently of each other haveone of the meanings of R^(a) and R^(b) in formula 3.

In the case of the polymeric formulae described herein, such as formulae1 to 8, the polymers may be terminated by any terminal group, that isany end-capping or leaving group, including H.

In the case of a block-copolymer, each monomer A, B, . . . Z may be aconjugated oligomer or polymer comprising a number, for example 2 to 50,of the units of formulae 3-8. The semiconducting binder preferablyincludes: arylamine, fluorene, thiophene, spiro bifluorene and/oroptionally substituted aryl (for example phenylene) groups, morepreferably arylamine, most preferably triarylamine groups. Theaforementioned groups may be linked by further conjugating groups, forexample vinylene.

In addition, it is preferred that the semiconducting binder comprises apolymer (either a homo-polymer or copolymer, including block-copolymer)containing one or more of the aforementioned arylamine, fluorene,thiophene and/or optionally substituted aryl groups. A preferredsemiconducting binder comprises a homo-polymer or copolymer (includingblock-copolymer) containing arylamine (preferably triarylamine) and/orfluorene units. Another preferred semiconducting binder comprises ahomo-polymer or co-polymer (including block-copolymer) containingfluorene and/or thiophene units.

The semiconducting binder may also contain carbazole or stilbene repeatunits. For example, polyvinylcarbazole, polystilbene or their copolymersmay be used. The semiconducting binder may optionally contain DBBDTsegments (for example repeat units as described for formula 1 above) toimprove compatibility with the soluble compounds of formula.

Very preferred semiconducting binders for use in the organicsemiconductor formulation according to the present invention arepoly(9-vinylcarbazole) and PTAA1, a polytriarylamine of the followingformula

wherein m is as defined in formula 1.

For application of the semiconducting layer in p-channel FETs, it isdesirable that the semiconducting binder should have a higher ionisationpotential than the semiconducting compound of formula I, otherwise thebinder may form hole traps. In n-channel materials the semiconductingbinder should have lower electron affinity than the n-type semiconductorto avoid electron trapping.

The formulation according to the present invention may be prepared by aprocess which comprises:

-   (i) first mixing a compound of formula I and an organic binder or a    precursor thereof. Preferably the mixing comprises mixing the two    components together in a solvent or solvent mixture,-   (ii) applying the solvent(s) containing the compound of formula I    and the organic binder to a substrate; and optionally evaporating    the solvent(s) to form a solid organic semiconducting layer    according to the present invention,-   (iii) and optionally removing the solid layer from the substrate or    the substrate from the solid layer.

In step (i) the solvent may be a single solvent or the compound offormula I and the organic binder may each be dissolved in a separatesolvent followed by mixing the two resultant solutions to mix thecompounds.

The binder may be formed in situ by mixing or dissolving a compound offormula I in a precursor of a binder, for example a liquid monomer,oligomer or crosslinkable polymer, optionally in the presence of asolvent, and depositing the mixture or solution, for example by dipping,spraying, painting or printing it, on a substrate to form a liquid layerand then curing the liquid monomer, oligomer or crosslinkable polymer,for example by exposure to radiation, heat or electron beams, to producea solid layer. If a preformed binder is used it may be dissolvedtogether with the compound of formula I in a suitable solvent, and thesolution deposited for example by dipping, spraying, painting orprinting it on a substrate to form a liquid layer and then removing thesolvent to leave a solid layer. It will be appreciated that solvents arechosen which are able to dissolve both the binder and the compound offormula I, and which upon evaporation from the solution blend give acoherent defect free layer.

Suitable solvents for the binder or the compound of formula I can bedetermined by preparing a contour diagram for the material as describedin ASTM Method D 3132 at the concentration at which the mixture will beemployed. The material is added to a wide variety of solvents asdescribed in the ASTM method.

It will also be appreciated that in accordance with the presentinvention the formulation may also comprise two or more compounds offormula I and/or two or more binders or binder precursors, and that theprocess for preparing the formulation may be applied to suchformulations.

Examples of suitable and preferred organic solvents include, withoutlimitation, dichloromethane, trichloromethane, monochlorobenzene,o-dichlorobenzene, tetrahydrofuran, anisole, morpholine, toluene,o-xylene, m-xylene, p-xylene, 1,4-dioxane, acetone, methylethylketone,1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane,ethyl acetate, n-butyl acetate, dimethylformamide, dimethylacetamide,dimethylsulfoxide, tetralin, decalin, indane and/or mixtures thereof.

After the appropriate mixing and ageing, solutions are evaluated as oneof the following categories: complete solution, borderline solution orinsoluble. The contour line is drawn to outline the solubilityparameter-hydrogen bonding limits dividing solubility and insolubility.‘Complete’ solvents falling within the solubility area can be chosenfrom literature values such as published in “Crowley, J. D., Teague, G.S. Jr and Lowe, J. W. Jr., J. Paint Tech., 1966, 38(496), 296”. Solventblends may also be used and can be identified as described in “Solvents,W. H. Ellis, Federation of Societies for Coatings Technology, p 9-10,1986”. Such a procedure may lead to a blend of ‘non’ solvents that willdissolve both the binder and the compound of formula I, although it isdesirable to have at least one true solvent in a blend.

Especially preferred solvents for use in the formulation according tothe present invention, with insulating or semiconducting binders andmixtures thereof, are xylene(s), toluene, tetralin ando-dichlorobenzene.

The proportions of binder to the compound of formula I in theformulation or layer according to the present invention are typically20:1 to 1:20 by weight, preferably 10:1 to 1:10 more preferably 5:1 to1:5, still more preferably 3:1 to 1:3 further preferably 2:1 to 1:2 andespecially 1:1. Surprisingly and beneficially, dilution of the compoundof formula I in the binder has been found to have little or nodetrimental effect on the charge mobility, in contrast to what wouldhave been expected from the prior art.

In accordance with the present invention it has further been found thatthe level of the solids content in the organic semiconducting layerformulation is also a factor in achieving improved mobility values forelectronic devices such as OFETs. The solids content of the formulationis commonly expressed as follows:

${{Solids}\mspace{14mu}{content}\mspace{11mu}(\%)} = {\frac{a + b}{a + b + c} \times 100}$wherein a=mass of compound of formula I, b=mass of binder and c=mass ofsolvent.

The solids content of the formulation is preferably 0.1 to 10% byweight, more preferably 0.5 to 5% by weight.

Surprisingly and beneficially, dilution of the compound of formula I inthe binder has been found to have little or no effect on the chargemobility, in contrast to what would have been expected from the priorart.

The compounds according to the present invention can also be used inmixtures or blends, for example together with other compounds havingcharge-transport, semiconducting, electrically conducting,photoconducting and/or light emitting semiconducting properties. Thus,another aspect of the invention relates to a mixture or blend comprisingone or more compounds of formula I and one or more further compoundshaving one or more of the above-mentioned properties. These mixtures canbe prepared by conventional methods that are described in prior art andknown to the skilled person. Typically the compounds are mixed with eachother or dissolved in suitable solvents and the solutions combined.

The formulations according to the present invention can additionallycomprise one or more further components like for example surface-activecompounds, lubricating agents, wetting agents, dispersing agents,hydrophobing agents, adhesive agents, flow improvers, defoaming agents,deaerators, diluents which may be reactive or non-reactive, auxiliaries,colourants, dyes or pigments, sensitizers, stabilizers, nanoparticles orinhibitors.

It is desirable to generate small structures in modern microelectronicsto reduce cost (more devices/unit area), and power consumption.Patterning of the layer of the invention may be carried out byphotolithography or electron beam lithography.

Liquid coating of organic electronic devices such as field effecttransistors is more desirable than vacuum deposition techniques. Theformulations of the present invention enable the use of a number ofliquid coating techniques. The organic semiconductor layer may beincorporated into the final device structure by, for example and withoutlimitation, dip coating, spin coating, ink jet printing, letter-pressprinting, screen printing, doctor blade coating, roller printing,reverse-roller printing, offset lithography printing, flexographicprinting, web printing, spray coating, brush coating or pad printing.The present invention is particularly suitable for use in spin coatingthe organic semiconductor layer into the final device structure.

Selected formulations of the present invention may be applied toprefabricated device substrates by ink jet printing or microdispensing.Preferably industrial piezoelectric print heads such as but not limitedto those supplied by Aprion, Hitachi-Koki, InkJet Technology, On TargetTechnology, Picojet, Spectra, Trident, Xaar may be used to apply theorganic semiconductor layer to a substrate. Additionally semi-industrialheads such as those manufactured by Brother, Epson, Konica, SeikoInstruments Toshiba TEC or single nozzle microdispensers such as thoseproduced by Microdrop and Microfab may be used.

In order to be applied by ink jet printing or microdispensing, themixture of the compound of formula I and the binder should be firstdissolved in a suitable solvent. Solvents must fulfil the requirementsstated above and must not have any detrimental effect on the chosenprint head.

Additionally, solvents should have boiling points >100° C.,preferably >140° C. and more preferably >150° C. in order to preventoperability problems caused by the solution drying out inside the printhead. Suitable solvents include substituted and non-substituted xylenederivatives, di-C₁₋₂-alkyl formamide, substituted and non-substitutedanisoles and other phenol-ether derivatives, substituted heterocyclessuch as substituted pyridines, pyrazines, pyrimidines, pyrrolidinones,substituted and non-substituted N,N-di-C₁₋₂-alkylanilines and otherfluorinated or chlorinated aromatics.

A preferred solvent for depositing a formulation according to thepresent invention by ink jet printing comprises a benzene derivativewhich has a benzene ring substituted by one or more substituents whereinthe total number of carbon atoms among the one or more substituents isat least three. For example, the benzene derivative may be substitutedwith a propyl group or three methyl groups, in either case there beingat least three carbon atoms in total. Such a solvent enables an ink jetfluid to be formed comprising the solvent with the binder and thecompound of formula I which reduces or prevents clogging of the jets andseparation of the components during spraying. The solvent(s) may includethose selected from the following list of examples: dodecylbenzene,1-methyl-4-tert-butylbenzene, terpineol limonene, isodurene,terpinolene, cymene, diethylbenzene. The solvent may be a solventmixture, that is a combination of two or more solvents, each solventpreferably having a boiling point >100° C., more preferably >140° C.Such solvent(s) also enhance film formation in the layer deposited andreduce defects in the layer.

The ink jet fluid (that is mixture of solvent, binder and semiconductingcompound) preferably has a viscosity at 20° C. of 1 to 100 mPa·s, morepreferably 1 to 50 mPa·s and most preferably 1 to 30 mPa·s.

The use of the binder in the present invention allows tuning theviscosity of the coating solution, to meet the requirements ofparticular print heads. The semiconducting layer of the presentinvention is typically at most 1 micron (=1 μm) thick, although it maybe thicker if required. The exact thickness of the layer will depend,for example, upon the requirements of the electronic device in which thelayer is used. For use in an OFET or OLED, the layer thickness maytypically be 500 nm or less.

In the semiconducting layer of the present invention there may be usedtwo or more different compounds of formula I. Additionally oralternatively, in the semiconducting layer there may be used two or moreorganic binders of the present invention.

As mentioned above, the invention further provides a process forpreparing the organic semiconducting layer which comprises (i)depositing on a substrate a liquid layer of a formulation whichcomprises one or more compounds of formula I, one or more organicbinders or precursors thereof and optionally one or more solvents, and(ii) forming from the liquid layer a solid layer which is the organicsemiconducting layer.

In the process, the solid layer may be formed by evaporation of thesolvent and/or by reacting the binder resin precursor (if present) toform the binder resin in situ. The substrate may include any underlyingdevice layer, electrode or separate substrate such as silicon wafer orpolymer substrate for example.

In a particular embodiment of the present invention, the binder may bealignable, for example capable of forming a liquid crystalline phase. Inthat case the binder may assist alignment of the compound of formula I,for example such that their aromatic core is preferentially alignedalong the direction of charge transport. Suitable processes for aligningthe binder include those processes used to align polymeric organicsemiconductors and are described in prior art, for example in US2004/0248338 A1.

The formulation according to the present invention can additionallycomprise one or more further components like for example surface-activecompounds, lubricating agents, wetting agents, dispersing agents,hydrophobing agents, adhesive agents, flow improvers, defoaming agents,deaerators, diluents, reactive or non-reactive diluents, auxiliaries,colourants, dyes or pigments, furthermore, especially in casecrosslinkable binders are used, catalysts, sensitizers, stabilizers,inhibitors, chain-transfer agents or co-reacting monomers.

The present invention also provides the use of the semiconductingcompound, formulation or layer in an electronic device. The formulationmay be used as a high mobility semiconducting material in variousdevices and apparatus. The formulation may be used, for example, in theform of a semiconducting layer or film. Accordingly, in another aspect,the present invention provides a semiconducting layer for use in anelectronic device, the layer comprising the formulation according to theinvention. The layer or film may be less than about 30 microns. Forvarious electronic device applications, the thickness may be less thanabout 1 micron thick. The layer may be deposited, for example on a partof an electronic device, by any of the aforementioned solution coatingor printing techniques.

The compounds and formulations according to the present invention areuseful as charge transport, semiconducting, electrically conducting,photoconducting or light mitting materials in optical, electrooptical,electronic, electroluminescent or photoluminescent components ordevices. Especially preferred devices are OFETs, TFTs, ICs, logiccircuits, capacitors, RFID tags, OLEDs, OLETs, OPEDs, OPVs, solar cells,laser diodes, photoconductors, photodetectors, electrophotographicdevices, electrophotographic recording devices, organic memory devices,sensor devices, charge injection layers, Schottky diodes, planarisinglayers, antistatic films, conducting substrates and conducting patterns.In these devices, the compounds of the present invention are typicallyapplied as thin layers or films.

For example, the compound or formulation may be used as a layer or film,in a field effect transistor (FET) for example as the semiconductingchannel, organic light emitting diode (OLED) for example as a hole orelectron injection or transport layer or electroluminescent layer,photodetector, chemical detector, photovoltaic cell (PVs), capacitorsensor, logic circuit, display, memory device and the like. The compoundor formulation may also be used in electrophotographic (EP) apparatus.

The compound or formulation is preferably solution coated to form alayer or film in the aforementioned devices or apparatus to provideadvantages in cost and versatility of manufacture. The improved chargecarrier mobility of the compound or formulation of the present inventionenables such devices or apparatus to operate faster and/or moreefficiently.

Especially preferred electronic device are OFETs, OLEDs and OPV devices,in particular bulk heterojunction (BHJ) OPV devices. In an OFET, forexample, the active semiconductor channel between the drain and sourcemay comprise the layer of the invention. As another example, in an OLEDdevice, the charge (hole or electron) injection or transport layer maycomprise the layer of the invention.

For use in OPV devices the polymer according to the present invention ispreferably used in a formulation that comprises or contains, morepreferably consists essentially of, very preferably exclusively of, ap-type (electron donor) semiconductor and an n-type (electron acceptor)semiconductor.

The p-type semiconductor is constituted by a compound according to thepresent invention. The n-type semiconductor can be an inorganic materialsuch as zinc oxide or cadmium selenide, or an organic material such as afullerene derivate, for example (6,6)-phenyl-butyric acid methyl esterderivatized methano C₆₀ fullerene, also known as “PCBM” or “C₆₀PCBM”, asdisclosed for example in G. Yu, J. Gao, J. C. Hummelen, F. Wudl, A. J.Heeger, Science 1995, 270, 1789 and having the structure shown below, oran structural analogous compound with e.g. a C₇₀ fullerene group(C₇₀PCBM), or a polymer (see for example Coakley, K. M. and McGehee, M.D. Chem. Mater. 2004, 16, 4533).

A preferred material of this type is a blend or mixture of an acenecompound according to the present invention with a C₆₀ or C₇₀ fullereneor modified fullerene like PCBM. Preferably the ratio acene:fullerene isfrom 2:1 to 1:2 by weight, more preferably from 1.2:1 to 1:1.2 byweight, most preferably 1:1 by weight. For the blended mixture, anoptional annealing step may be necessary to optimize blend morpohologyand consequently OPV device performance.

The OPV device can for example be of any type known from the literature[see e.g. Waldauf et al., Appl. Phys. Lett., 2006, 89, 233517].

A first preferred OPV device according to the invention comprises:

-   -   a low work function electrode (for example a metal, such as        aluminum), and a high work function electrode (for example ITO),        one of which is transparent,    -   a layer (also referred to as “active layer”) comprising a hole        transporting material and an electron transporting material,        preferably selected from OSC materials, situated between the        electrodes; the active layer can exist for example as a bilayer        or two distinct layers or blend or mixture of p-type and n-type        semiconductor, forming a bulk heterjunction (BHJ) (see for        example Coakley, K. M. and McGehee, M. D. Chem. Mater. 2004, 16,        4533),    -   an optional conducting polymer layer, for example comprising a        blend of PEDOT:PSS        (poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)),        situated between the active layer and the high work function        electrode, to modify the work function of the high work function        electrode to provide an ohmic contact for holes,    -   an optional coating (for example of LiF) on the side of the low        workfunction electrode facing the active layer, to provide an        ohmic contact for electrons.

A second preferred OPV device according to the invention is an invertedOPV device and comprises:

-   -   a low work function electrode (for example a metal, such as        gold), and a high work function electrode (for example ITO), one        of which is transparent,    -   a layer (also referred to as “active layer”) comprising a hole        transporting material and an electron transporting material,        preferably selected from OSC materials, situated between the        electrodes; the active layer can exist for example as a bilayer        or two distinct layers or blend or mixture of p-type and n-type        semiconductor, forming a BHJ,    -   an optional conducting polymer layer, for example comprising a        blend of PEDOT:PSS, situated between the active layer and the        low work function electrode to provide an ohmic contact for        electrons,    -   an optional coating (for example of TiO_(x)) on the side of the        high workfunction electrode facing the active layer, to provide        an ohmic contact for holes.

In the OPV devices of the present invent invention the p-type and n-typesemiconductor materials are preferably selected from the materials, likethe p-type compound/fullerene systems, as described above. If thebilayer is a blend an optional annealing step may be necessary tooptimize device performance.

The compound, formulation and layer of the present invention are alsosuitable for use in an OFET as the semiconducting channel. Accordingly,the invention also provides an OFET comprising a gate electrode, aninsulating (or gate insulator) layer, a source electrode, a drainelectrode and an organic semiconducting channel connecting the sourceand drain electrodes, wherein the organic semiconducting channelcomprises a compound, formulation or organic semiconducting layeraccording to the present invention. Other features of the OFET are wellknown to those skilled in the art.

OFETs where an OSC material is arranged as a thin film between a gatedielectric and a drain and a source electrode, are generally known, andare described for example in U.S. Pat. No. 5,892,244, U.S. Pat. No.5,998,804, U.S. Pat. No. 6,723,394 and in the references cited in thebackground section. Due to the advantages, like low cost productionusing the solubility properties of the compounds according to theinvention and thus the processibility of large surfaces, preferredapplications of these FETs are such as integrated circuitry, TFTdisplays and security applications.

The gate, source and drain electrodes and the insulating andsemiconducting layer in the OFET device may be arranged in any sequence,provided that the source and drain electrode are separated from the gateelectrode by the insulating layer, the gate electrode and thesemiconductor layer both contact the insulating layer, and the sourceelectrode and the drain electrode both contact the semiconducting layer.

An OFET device according to the present invention preferably comprises:

-   -   a source electrode,    -   a drain electrode,    -   a gate electrode,    -   a semiconducting layer,    -   one or more gate insulator layers,    -   optionally a substrate.        wherein the semiconductor layer preferably comprises a compound        or formulation as described above and below.

The OFET device can be a top gate device or a bottom gate device.Suitable structures and manufacturing methods of an OFET device areknown to the skilled in the art and are described in the literature, forexample in US 2007/0102696 A1.

The gate insulator layer preferably comprises a fluoropolymer, like e.g.the commercially available Cytop 809M® or Cytop 107M® (from AsahiGlass). Preferably the gate insulator layer is deposited, e.g. byspin-coating, doctor blading, wire bar coating, spray or dip coating orother known methods, from a formulation comprising an insulator materialand one or more solvents with one or more fluoro atoms (fluorosolvents),preferably a perfluorosolvent. A suitable perfluorosolvent is e.g. FC75®(available from Acros, catalogue number 12380). Other suitablefluoropolymers and fluorosolvents are known in prior art, like forexample the perfluoropolymers Teflon AF®, 1600 or 2400 (from DuPont) orFluoropel® (from Cytonix) or the perfluorosolvent FC 43® (Acros, No.12377). Especially preferred are organic dielectric materials having alow permittivity (or dielectric constant) from 1.0 to 5.0, verypreferably from 1.8 to 4.0 (“low k materials”), as disclosed for examplein US 2007/0102696 A1 or U.S. Pat. No. 7,095,044.

In security applications, OFETs and other devices with semiconductingmaterials according to the present invention, like transistors ordiodes, can be used for RFID tags or security markings to authenticateand prevent counterfeiting of documents of value like banknotes, creditcards or ID cards, national ID documents, licenses or any product withmonetry value, like stamps, tickets, shares, cheques etc.

Alternatively, the materials according to the invention can be used inOLEDs, e.g. as the active display material in a flat panel displayapplications, or as backlight of a flat panel display like e.g. a liquidcrystal display. Common OLEDs are realized using multilayer structures.An emission layer is generally sandwiched between one or moreelectron-transport and/or hole-transport layers. By applying an electricvoltage electrons and holes as charge carriers move towards the emissionlayer where their recombination leads to the excitation and henceluminescence of the lumophor units contained in the emission layer. Theinventive compounds, materials and films may be employed in one or moreof the charge transport layers and/or in the emission layer,corresponding to their electrical and/or optical properties. Furthermoretheir use within the emission layer is especially advantageous, if thecompounds, materials and films according to the invention showelectroluminescent properties themselves or comprise electroluminescentgroups or compounds. The selection, characterization as well as theprocessing of suitable monomeric, oligomeric and polymeric compounds ormaterials for the use in OLEDs is generally known by a person skilled inthe art, see, e.g., Müller, Synth. Metals, 2000, 111-112, 31, Alcala, J.Appl. Phys., 2000, 88, 7124 and the literature cited therein.

According to another use, the materials according to this invention,especially those showing photoluminescent properties, may be employed asmaterials of light sources, e.g. in display devices, as described in EP0 889 350 A1 or by C. Weder et al., et al., Science, 1998, 279, 835-837.

A further aspect of the invention relates to both the oxidised andreduced form of the compounds according to this invention. Either lossor gain of electrons results in formation of a highly delocalised ionicform, which is of high conductivity. This can occur on exposure tocommon dopants. Suitable dopants and methods of doping are known tothose skilled in the art, e.g. from EP 0 528 662, U.S. Pat. No.5,198,153 or WO 96/21659.

The doping process typically implies treatment of the semiconductormaterial with an oxidating or reducing agent in a redox reaction to formdelocalised ionic centres in the material, with the correspondingcounterions derived from the applied dopants. Suitable doping methodscomprise for example exposure to a doping vapor in the atmosphericpressure or at a reduced pressure, electrochemical doping in a solutioncontaining a dopant, bringing a dopant into contact with thesemiconductor material to be thermally diffused, and ion-implantantionof the dopant into the semiconductor material.

When electrons are used as carriers, suitable dopants are for examplehalogens (e.g., I₂, Cl₂, Br₂, ICl, ICl₃, IBr and IF), Lewis acids (e.g.,PF₅, AsF₅, SbF₅, BF₃, BCl₃, SbCl₅, BBr₃ and SO₃), protonic acids,organic acids, or amino acids (e.g., HF, HCl, HNO₃, H₂SO₄, HClO₄, FSO₃Hand ClSO₃H), transition metal compounds (e.g., FeCl₃, FeOCl, Fe(ClO₄)₃,Fe(4-CH₃C₆H₄SO₃)₃, TiCl₄, ZrCl₄, HfCl₄, NbF₅, NbCl₅, TaCl₅, MoF₅, MoCl₅,WF₅, WCl₆, UF₆ and LnCl₃ (wherein Ln is a lanthanoid), anions (e.g.,Cl⁻, Br⁻, I⁻, I₃ ⁻, HSO₄ ⁻, SO₄ ²⁻, NO₃ ⁻, ClO₄ ⁻, BF₄ ⁻, PF₆ ⁻, AsF₆ ⁻,SbF₆ ⁻, FeCl₄ ⁻, Fe(CN)₆ ³⁻, and anions of various sulfonic acids, suchas aryl-SO₃ ⁻). When holes are used as carriers, examples of dopants arecations (e.g., H⁺, Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺), alkali metals (e.g., Li,Na, K, Rb, and Cs), alkaline-earth metals (e.g., Ca, Sr, and Ba), O₂,XeOF₄, (NO₂)⁺ (SbF₆ ⁻), (NO₂ ⁺) (SbCl₆ ⁻), (NO₂ ⁺) (BF₄ ⁻), AgClO₄,H₂IrCl₆, La(NO₃)₃.6H₂O, FSP₂OOSO₂F, Eu, acetylcholine, R₄N⁺, (R is analkyl group), R₄P⁺ (R is an alkyl group), R₆As⁺ (R is an alkyl group),and R₃S⁺ (R is an alkyl group).

The conducting form of the compounds of the present invention can beused as an organic “metal” in applications including, but not limitedto, charge injection layers and ITO planarising layers in OLEDapplications, films for flat panel displays and touch screens,antistatic films, printed conductive substrates, patterns or tracts inelectronic applications such as printed circuit boards and condensers.

The compounds and formulations according to the present invention amyalso be suitable for use in organic plasmon-emitting diodes (OPEDs), asdescribed for example in Koller et al., Nat. Photonics, 2008, 2, 684.

According to another use, the materials according to the presentinvention can be used alone or together with other materials in or asalignment layers in LCD or OLED devices, as described for example in US2003/0021913. The use of charge transport compounds according to thepresent invention can increase the electrical conductivity of thealignment layer. When used in an LCD, this increased electricalconductivity can reduce adverse residual dc effects in the switchableLCD cell and suppress image sticking or, for example in ferroelectricLCDs, reduce the residual charge produced by the switching of thespontaneous polarisation charge of the ferroelectric LCs. When used inan OLED device comprising a light emitting material provided onto thealignment layer, this increased electrical conductivity can enhance theelectroluminescence of the light emitting material. The compounds ormaterials according to the present invention having mesogenic or liquidcrystalline properties can form oriented anisotropic films as describedabove, which are especially useful as alignment layers to induce orenhance alignment in a liquid crystal medium provided onto saidanisotropic film. The materials according to the present invention mayalso be combined with photoisomerisable compounds and/or chromophoresfor use in or as photoalignment layers, as described in US 2003/0021913A1.

According to another use the materials according to the presentinvention, especially their water-soluble derivatives (for example withpolar or ionic side groups) or ionically doped forms, can be employed aschemical sensors or materials for detecting and discriminating DNAsequences. Such uses are described for example in L. Chen, D. W.McBranch, H. Wang, R. Helgeson, F. Wudl and D. G. Whitten, Proc. Natl.Acad. Sci. U.S.A. 1999, 96, 12287; D. Wang, X. Gong, P. S. Heeger, F.Rininsland, G. C. Bazan and A. J. Heeger, Proc. Natl. Acad. Sci. U.S.A.,2002, 99, 49; N. DiCesare, M. R. Pinot, K. S. Schanze and J. R.Lakowicz, Langmuir, 2002, 18, 7785; D. T. McQuade, A. E. Pullen, T. M.Swager, Chem. Rev. 2000, 100, 2537.

Unless the context clearly indicates otherwise, as used herein pluralforms of the terms herein are to be construed as including the singularform and vice versa.

Throughout the description and claims of this specification, the words“comprise” and “contain” and variations of the words, for example“comprising” and “comprises”, mean “including but not limited to”, andare not intended to (and do not) exclude other components.

It will be appreciated that variations to the foregoing embodiments ofthe invention can be made while still falling within the scope of theinvention. Each feature disclosed in this specification, unless statedotherwise, may be replaced by alternative features serving the same,equivalent or similar purpose. Thus, unless stated otherwise, eachfeature disclosed is one example only of a generic series of equivalentor similar features.

All of the features disclosed in this specification may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. In particular, thepreferred features of the invention are applicable to all aspects of theinvention and may be used in any combination. Likewise, featuresdescribed in non-essential combinations may be used separately (not incombination).

It will be appreciated that many of the features described above,particularly of the preferred embodiments, are inventive in their ownright and not just as part of an embodiment of the present invention.Independent protection may be sought for these features in addition toor alternative to any invention presently claimed.

The invention will now be described in more detail by reference to thefollowing examples, which are illustrative only and do not limit thescope of the invention.

Example 1

Compound 1 was prepared as described below, and as schematicallydepicted in Scheme 1.

5-Iodo-2,3-thiophenediacetal (B)

The solution of the diacetal of 2,3-thiophenedicarboxaldehyde (34.24 g,150.00 mmol) in anhydrous THF (300 cm³) was cooled to −78° C. and n-BuLi(2.5M in hexanes, 62 cm³, 155.00 mmol) was added dropwise over 30minutes. The reaction mixture was stirred at −78° C. for 1.5 hoursfollowed by the addition of iodine (40.06 g, 157.50 mmol) in oneportion. The cooling bath was removed and the mixture was stirred at 20°C. for 15 hours. Saturated sodium thiosulfate solution (50 cm³) wasadded slowly and the mixture was stirred at 20° C. for 30 minutes. Theorganic layer was separated and washed with brine once. The aqueouslayer was extracted with diethyl ether (2×50 cm³) and the combined withthe organic layer.

The organic solution was dried over MgSO₄ then concentrated in vacuo toyield 5-iodo-2,3-thiophenediacetal as a yellow oil, which solidified asan off white solid (50.96 g, 90%). ¹H-NMR (CDCl₃, 300 MHz): δ (ppm)=4.0(m, 4H), 4.1 (m, 4H), 5.96 (s, 1H), 6.29 (s, 1H), 7.24 (s, 1H).

5-iodo-2,3-thiophenedicarboxaldehyde (C)

To the stirred solution of 5-iodo-2,3-thiophenediacetal (50.96 g, 135.11mmol) in acetic acid (100 cm³) was added 32% hydrochloric acid dropwise.The reaction mixture was stirred at 20° C. for 1 hour. Water (200 cm³)was added slowly. The precipitate was collected by suction filtrationand then dissolved in warm chloroform before purification by flashchromatography (eluent: DCM) to yield5-iodo-2,3-thiophenedicarbox-aldehyde as a yellow solid (29.56 g, 82%).¹H-NMR (CDCl₃, 300 MHz): δ (ppm)=7.77 (s, 1H), 10.23 (s, 1H), 10.33 (s,1H). ¹³C-NMR (CDCl₃, 75 MHz): δ (ppm)=86.3, 139.3, 144.3, 152.6, 181.1,183.1.

2,7-diiodo-anthra[2,3-b:7,6-b]dithiophene-11,12-Quinone (D)

5-Iodo-2,3-thiophenedicarboxaldehyde (20.00 g, 75.15 mmol) and1,4-cyclohexandione (4.25 g, 37.12 mmol) were dissoved in IMS(industrial methylated spirits) (600 cm³) by warming and stirring, andthen cooled to 20° C. with a water bath. 5% KOH solution (7.5 cm³) wasadded in one portion under nitrogen with vigorous stirring. The reactionmixture was stirred at 20° C. for 30 minutes and the precipitate formedwas collected by suction filtration, washed with IMS, water, IMS, thenacetone, and dried in the vacuum oven at 40° C. overnight to yield2,8-diiodo-anthra[2,3-b:7,6-b′]dithiophene-5,11-dione (18.39 g, 87%).The solid was directly used for the following reactions without furtherpurification.

2,8-Iodo-5,11-dihydro-5,11-bis(triisopropylsilylethynyl)anthradithiophene-5,11-diol(E1)

To the ice-water cooled solution of triisopropylsilylacetylene (8.50cm³, 36.00 mmol) in anhydrous dioxane (60 cm³) was added n-BuLi (2.5M inhexanes, 14.4 cm³, 36.00 mmol) dropwise over 10 minutes. The reactionmixture was stirred at 20° C. for an additional 30 minutes.2,8-Diiodo-anthra[2,3-b:7,6-b]dithiophene-5,11-dione (5.15 g, 9.00 mmol)was added in one portion and the suspension was stirred at 20° C. for0.5 hours and then at 60° C. for an additional 2 hours. The reactionmixture was cooled with an ice-bath. 1M HCl (30 cm³) was added and theupper organic layer was separated and the aqueous phase was extractedwith diethyl ether (30 cm³). The combined organic solution wasconcentrated in vacuo and the residue was purified by flashchromatography (eluent: 1:1 DCM:petroleum ether 40-60) to yield anoff-white solid, which was crystallised from petroleum ether 80-100 toyield off-white needles (3.72 g). This solid was the anti isomerproduct. The eluent was changed to pure DCM and the syn isomer productwas collected as a yellow solid, which was crystallised from petroeumether 80-100 to yield yellow crystals (1.34 g). The combined yield ofboth isomer products was 60%. Both isomer products showed similar NMRspectra and when aromatised further on in the synthesis route yieldedidentical products. ¹H-NMR (CDCl₃, 300 MHz, syn-isomer): δ (ppm)=1.24(m, 21H), 4.20 (m, 1H), 7.54 (s, 1H), 8.60 (s, 1H), 8.66 (s, 1H).

2,8-Bis(2-thienyl)-5,11-dihydro-5,11-bis(triisopropylsilylethynyl)anthradithiophene-5,11-diol(F)

A solution of2,8-iodo-5,11-dihydro-5,11-bis(triisopropylsilylethynyl)-anthradithiophene-5,11-diol(1.41 g, 1.50 mmol) and 2-(tributylstannyl)-thiophene (1.68 g, 4.50mmol) in anhydrous THF (40 cm³) was degassed with bubbling nitrogen for20 minutes. Pd(PPh₃)₃Cl₂ (105 mg, 0.15 mmol) was added and the reactionmixture was stirred at 67° C. for 7 hours. The solution was concentratedin vacuo and the residue was purified by flash chromatography (eluent:1:1 DCM:petroleum ether 40-60) to yield both fractions of2,8-bis(thienyl)-5,11-dihydro-5,11-bis(triisopropylsilylethynyl)-anthradithiophene-5,11-diolas a pale-red solid and2,8-bis(thienyl)-5,11-bis(triisopropylsilylethynyl)anthradithiophene (1)as dark red solid due to aromatisation induced on the acidic silica gel.The2,8-bis(2-thienyl)-5,11-dihydro-5,11-bis(triisopropylsilylethynyl)anthradithiophene-5,11-diolfraction was triturated with petroleum ether 40-60 and suction filteredto yield an off-white solid (0.40 g, 31%). ¹H-NMR (CDCl₃, 300 MHz): δ(ppm) 1.07 (m, 21H), 3.19 (t, 1H), 7.08 (dd, 1H), 7.34 (m, 2H), 7.43 (s,1H), 8.51 (s, 1H), 8.59 (s, 1H).

2,8-Bis(2-thienyl)-5,11-bis(triisopropylsilylethynyl)anthradithiophene(1)

To the solution of2,8-bis(thienyl)-5,11-dihydro-5,11-bis(triisopropylsilylethynyl)anthradithiophene-5,11-diol(0.40 g, 0.46 mmol) in THF (10 ml) was added a solution of tin(II)chloride (0.208 g, 0.92 mmol) in 1N HCl (5 ml) and the mixture wasstirred at 20° C. for 30 min to yield a purple-brown suspension.Methanol (ca 30 ml) was added and the solid was collected by suctionfiltration then washed with methanol to yield a dark-purple crystallinesolid. The solid was recrystallised from toluene-ethanol to yield yield2,8-bis(2-thienyl)-5,11-bis(triisopropylsilylethynyl)anthradithiophene(1) as a permaganate coloured crystalline solid (0.301 g, 79.9%). ¹H-NMR(CDCl₃, 300 MHz): δ (ppm)=1.35 (m, 21H), 7.10 (dd, 1H), 7.39 (m, 2H),8.99 (s, 1H), 9.05 (s, 1H).

Example 2

2,8-Bis(2-thienyl)-5,11-bis(triethylsilylethynyl)anthradithiophene (2)was prepared as described below, and as schematically depicted in Scheme1.

2,8-Iodo-5,11-dihydro-5,11-bis(triethylsilylethynyl)anthradithiophene-5,11-diol(E2)

2,8-iodo-5,11-dihydro-5,11-bis(triisopropylsilylethynyl)anthradithiophene-5,11-diol,the triethylsilyl analogue was synthesized by treating2,8-iodo-anthradithiophene-5,11-dione (2.86 g, 5.00 mmol) withtriethylsilyl-acetylene (3.60 cm³, 20.00 mmol) and n-BuLi (2.5M inhexanes, 8.0 cm³, 20.00 mmol) in anhydrous dioxane (40 cm³). The crudeproduct was purified by flash chromatography (eluent: 1:1 DCM:petroleumether 40-60) and recrystallisation from petroleum ether 80-100 to affordas2,8-iodo-5,11-dihydro-5,11-bis(triethylsilylethynyl)anthradithiophene-5,11-diolas rose-white crystals (1.18 g, 28%). ¹H-NMR (CDCl₃, 300 MHz): δ(ppm)=0.62 (m, 6H), 0.95 (m, 9H), 3.38 (s, 1H), 7.59 (s, 1H), 8.50 (m,2H).

2,8-Bis(2-thienyl)-5,11-bis(triethylsilylethynyl)anthradithiophene (2)

A solution of2,8-iodo-5,11-dihydro-5,11-bis(triethylsilylethynyl)anthradithiophene-5,11-diol(1.18 g, 1.38 mmol) and 2-tributylstannylthiophene (1.53 g, 4.10 mmol)in anhydrous DMF (30 cm³) was degassed with bubbling nitrogen for 20minutes. Pd(PPh₃)₃Cl₂ (97 mg, 0.14 mmol) was added and the reactionmixture was stirred at 75° C. for 17 hours. The DMF was removed invacuo. Methanol (40 cm³) was added and the precipitate solid wascollected by suction filtration and washed with methanol. The solid waspurified by flash chromatography (eluent: 1:1 DCM:petroleum ether 40-60)followed by dissolving in chloroform and precipitating into IMS to yield2,8-bis(2-thienyl)-5,11-bis(triethylsilylethynyl)anthradithiophene (2)as a dark purple micro-crystalline solid (0.59 g, 57%). ¹H-NMR (CDCl₃,300 MHz): δ (ppm)=0.95 (m, 6H), 1.27 (m, 9H), 7.09 (m, 1H), 7.37 (m,2H), 7.46 (s, 1H), 8.91 (d, 1H), 8.98 (d, 1H).

The single crystal structures of both compound 1 and compound 2 werebeen determined by X-ray diffraction. The thienyl-extended ADT cores inboth molecules remain essentially planar with small torsion angles alongthe 2,2′-bithiophene C—C bonds. For molecule 1, one of the angle is4.57° and other is −6.13°. The planarity of molecule 2 is even better,with a torsion angle of only ±1.61° on both sides.

Example 3

2,8-Bis(5-fluoro-2-thienyl)-5,11-bis(triisopropylsilylethynyl)anthradithiophene(3) was prepared as follows:

5-(2-Thienyl)-2,3-thiophenediacetal (G)

A solution of 5-iodo-2,3-thiophenediacetal (17.71 g, 50.00 mmol) and2-(tributylstannyl)thiophene (23.08 g, 60.00 mmol) in anhydrous DMF (120cm³) was degassed with bubbling nitrogen for 20 minutes. Pd(II)(PPh₃)₂O₂(1.76 g, 2.5 mmol) was added and the reaction mixture was stirred at 80°C. for 15.5 hours. The solvent was removed in vacuo and the residue waspurified by flash chromatogrpahy (eluent: 2:1 DCM:petroleum ether 40-60,then pure DCM) to yield 5-(2-thienyl)-2,3-thiophenediacetal as a yellowoil (14.12 g, 90%). ¹H-NMR (CDCl₃, 300 MHz): δ (ppm)=4.02 (m, 4H), 4.14(m, 4H), 6.01 (s, 1H), 6.34 (s, 1H), 7.00 (dd, J₁=5.1 Hz, J₂=3.7 Hz,1H), 7.16 (dd, J₁=3.7 Hz, J₂=1.1 Hz, 1H), 7.17 (s, 1H), 7.21 (dd, J₁=5.1Hz, J₂=1.1 Hz, 1H).

5-(5-Fluoro-2-thienyl)-2,3-thiophenediacetal (H)

To a stirred solution of 5-(2-thienyl)-2,3-thiophenediacetal (12.58 g,40 mmol) in anhydrous THF (150 cm³) was added n-BuLi (2.5 M in hexanes,18.00 cm³, 45.00 mmol) dropwise at −78° C. over 20 minutes. The solutionwas stirred at at −78° C. for an additional 1.5 hours.N-Fluorobis(phenyl-sulfonyl)amine (15.14 g, 48.00 mmol) was added in oneportion as a solid and the reaction mixture was stirred at −78° C. for10 minutes. The cooling bath was removed and the reaction mixture wasstirred at 20° C. for 20 hours. The suspension was cooled with anice-water bath and saturated ammonium chloride solution (100 cm³) wasadded portionwise under stirring to yield a two-layer liquid mixture.The organic layer was separated and washed once with water. The aqueousphase was extracted with ethyl acetate (2×50 cm³). The combined organicsolution was dried over magnesium sulphate and then concentrated invacuo to yield crude 5-(5-fluoro-2-thienyl)-2,3-thiophenediacetal (13.1g, 91%), which was used without further purification.

5-(5-Fluoro-2-thienyl)-2,3-thiophenedicarboxaldehyde (I)

To a stirred solution of 5-(5-fluoro-2-thienyl)-2,3-thiophenediacetal(3.50 g, 10.00 mmol) in acetic acid (30 cm³) was added 35% HCl (1.5 cm³)dropwise. The reaction mixture was stirred at 20° C. for 1 hour. Water(50 cm³) was added slowly. The precipitate formed was collected bysuction filtration before purification by flash chromatography (eluent:DCM) and recrystallisation from chloroform-cyclohexane to yield5-(5-fluoro-2-thienyl)-2,3-thiophenedicarboxaldehyde as green-yellowcrystals (1.49 g, 62%). ¹H-NMR (CDCl₃, 300 MHz): δ (ppm)=6.51 (dd,J₁=4.0 Hz, J₂=1.7 Hz, 1H), 7.01 (t, J=4.0 Hz, 1H), 7.48 (s, 1H), 10.31(s, 1H), 10.41 (s, 1H). ¹³C-NMR (CDCl₃, 75 MHz): δ (ppm)=109.12, 109.26,123.58, 123.63, 124.28, 144.27, 144.49, 145.73, 181.88, 184.31.

2,8-Bis(5-fluoro-2-thienyl)-anthradithiophene-5,11-dione (J)

5-(5-Fluoro-2-thienyl)-2,3-thiophenedicarboxaldehyde (1.22 g, 5.00 mmol)and 1,4-cyclohexanedione (0.29 g, 2.50 mmol) were dissolved in IMS (100cm³) with heating. A solution of 5% KOH (0.5 cm³) was added in oneportion. The reaction mixture was vigorously stirred under nitrogen andthe suspension formed was stirred for 2 minutes at 20° C. and then at78° C. for 20 minutes. The heating was stopped and the reaction mixturewas cooled back to 20° C. The precipitate was collected by suctionfiltration, washed with IMS, and dried in a vacuum oven at 40° C.overnight to yield2,8-bis(5-fluoro-2-thienyl)-anthradithiophene-5,11-dione as abrown-yellow solid (1.07 g, 82%).

2,8-Bis(5-fluoro-2-thienyl)-5,11-bis(triisopropylsilylethynyl)-anthradithiophene(3)

To the solution of the triisopropylsilylacetylene (1.18 cm³, 5.00 mmol)in anhydrous dioxane (30 cm³) at 0° C. was added dropwise n-BuLi (2.5 Min hexanes, 2.00 cm³, 5.00 mmol) over 10 minutes. The reaction mixturewas stirred at 20° C. for an additional 30 minutes.2,8-Bis(5-fluoro-2-thienyl)-anthradithiophene-5,11-dione (0.52 g, 1.00mmol) was added in one portion and the reaction mixture was sonicatedfor 20 minutes and then stirred at 65° C. for 3 hours. The reactionmixture was sonicated for an additional 5 minutes and then stirred at80° C. for 19 hours. After cooling to 20° C., tin(II) chloride (0.38 g,2.00 mmol) in 2N HCL (6 cm³) was added. The suspension formed wasstirred at 20° C. for 30 minutes followed by the addition of methanol(50 cm³). The precipitate was collected by suction filtration beforepurification by flash chromatography (eluent: 1:1 chloroform:petroleumether 40-60) to2,8-bis(5-fluoro-2-thienyl)-5,11-bis(triisopropylsilylethynyl)anthradithiophene(3) as a purple-red solid (0.36 g, 42%). ¹H-NMR (CDCl₃, 300 MHz): δ(ppm)=1.35 (m, 21H), 6.48 (dd, J₁=4.0 Hz, J₂=1.8 Hz, 1H), 6.99 (t, J=3.8Hz, 1H), 7.30 (s, 1H), 8.98 (s, 1H), 9.05 (s, 1H).

Example 4

2,8-Bis(3,5-difluorophenyl)-5,11-bis(triisopropylsilylethynyl)anthradithiophene(4) was prepared as follows:

2,8-Bis(3,5-difluorophenyl)-5,11-dihydro-5,11-bis(triisopropylsilylethynyl)-anthradithiophene-5,1-diol

A mixture of2,8-iodo-5,11-dihydro-5,11-bis(triisopropylsilylethynyl)-anthradithiophene-5,11-diol(1.34 g, 1.43 mmol), 3,5-difluorophenylboronic acid (0.71 g, 4.50 mmol)and Pd(PPh₃)₄ (99 mg, 0.086 mmol) in anhydrous THF (40 cm³) was degassedwith bubbling nitrogen through for 20 minutes. Sodium carbonate solution(2.0 M, 5 cm³) was added and the mixture was stirred at 70° C. for 17hours. The THF was removed in vacuo. Water (50 cm³) was added to theresidue and the precipitate was collected by suction filtration. Thecrude solid was dissolved in chloroform and purified by flashchromatography (eluent: DCM eluent) to yield2,8-bis(3,5-difluorophenyl)-5,11-dihydro-5,11-bis(triisopropylsilylethynyl)-anthradithiophene-5,1-diolas an off-white solid (0.85 g, 66%). ¹H-NMR (CDCl₃, 300 MHz): δ(ppm)=0.86 (m, 3H), 1.28 (m, 18H), 4.15 (s, 0.25H), 4.26 (s, 0.50H),4.37 (s, 0.25H), 6.78 (t, 0.25H), 6.81 (t, 0.5H), 6.84 (t, 0.25H), 7.26(d, J=2.2 Hz, 1H), 7.28 (d, J=2.2 Hz, 1H), 7.56 (s, 1H), 8.70 (d, J=1.5Hz, 1H), 8.77 (d, J=1.5 Hz, 1H).

2,8-Bis(3,5-difluorophenyl)-5,11-bis(triisopropylsilylethynyl)-anthradithiophene(4)

2,8-bis(3,5-difluorophenyl)-5,11-dihydro-5,11-bis(triisopropylsilylethynyl)-anthradithiophene-5,1-diol(0.85 g, 0.94 mmol) was dissolved in THF (20 cm³) and a solution oftin(II) chloride (0.45 g, 2.00 mmol) in 2.5N HCl (8 cm³) was added understirring. The resultant suspension was stirred at 20° C. for 45 minutes.Methanol (50 cm³) was added and the precipitate was collected by suctionfiltration. The crude solid was recrystallised from a mixture THF and2-butanone to yield2,8-bis(3,5-difluorophenyl)-5,11-bis(triisopropylsilylethynyl)anthradithiophene(4) as purple-red hairy crystals (0.77 g, 94%). ¹H-NMR (CDCl₃, 328K, 300MHz): δ (ppm)=1.38 (m, 21H), 6.83 (m, 1H), 7.31 (d, J=6.3 Hz, 2H), 7.63(s, 1H), 9.12 (s, 1H), 9.15 (s, 1H).

Example 5 Transistor Fabrication and Measurement

Top-gate thin-film organic field-effect transistors (OFETs) werefabricated on glass substrates with photolithographically defined Ausource-drain electrodes. A 0.5 wt. % solution of a 1:1 blend of thecompound and a polytriarylamine (PTAA) binder in ortho-dichlorobenzene(o-DCB) was spin-coated ontop. Next a fluoropolymer dielectric material(D139) was spin-coated ontop. Finally a photolithographically defined Augate electrode was deposited. The electrical characterization of thetransistor devices was carried out in ambient air atmosphere usingcomputer controlled Agilent 4155C Semiconductor Parameter Analyser.Charge carrier mobility in the saturation regime (μ_(sat)) wascalculated for the compound and the results are summarized in Table 1below. Field-effect mobility was calculated in the saturation regime(V_(d)>(V_(g)−V₀)) using equation (1):

$\begin{matrix}{\left( \frac{\mathbb{d}I_{d}^{sat}}{\mathbb{d}V_{g}} \right)_{V_{d}} = {\frac{{WC}_{i}}{L}{\mu^{sat}\left( {V_{g} - V_{0}} \right)}}} & (1)\end{matrix}$where W is the channel width, L the channel length, C_(i) thecapacitance of insulating layer, V_(g) the gate voltage, V₀ the turn-onvoltage, and μ_(sat) is the charge carrier mobility in the saturationregime. Turn-on voltage (V₀) was determined as the onset of source-draincurrent.

TABLE 1 Mobilties (μ_(sat)) for compounds (1)-(4) in top-gate OFETsCompound Mobility (μ_(sat))/cm²/Vs (1) 0.1 (2) 0.02 (3) 0.006 (4) 0.26

The invention claimed is:
 1. A compound of formula I

wherein one of Y¹ and Y² is —CH═ or ═CH— and the other is —X—, one of Y³and Y⁴ is —CH═ or ═CH— and the other is —X—, X is —O—, —S—, —Se— or—NR⁰—, R¹ and R² independently of each other denote: straight chain,branched or cyclic alkyl with 1 to 20 C-atoms, which is unsubstituted orsubstituted by one or more groups L, and wherein one or morenon-adjacent CH₂ groups are optionally replaced, in each caseindependently from one another, by —O—, —S—, —NR⁰—, —SiR⁰R⁰⁰—, —CY⁰═CY⁰—or —C≡C— in such a manner that O and/or S atoms are not linked directlyto one another; or denote aryl or heteroaryl with 4 to 20 ring atomswhich is unsubstituted or substituted by one or more groups L, Ar¹ andAr² independently of each other denote aryl or heteroaryl which isselected from the group consisting of: furan; thiophene; selenophene;N-pyrrole; pyrimidine; thiazole; thiadiazole; oxazole; oxadiazole;selenazole; bi-, tri- or tetracyclic groups containing one or more ofthe aforementioned rings and optionally containing one or more benzenerings, wherein the individual rings are connected by single bonds orfused with each other; thieno[3,2-b]thiophene;dithieno[3,2-b:2′,3′-d]thiophene;selenopheno[3,2-b]selenophene-2,5-diyl;selenopheno[2,3-b]selenophene-2,5-diyl;selenopheno[3,2-b]thiophene-2,5-diyl;selenopheno[2,3-b]thiophene-2,5-diyl;benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl; 2,2-dithiophene;2,2-diselenophene; dithieno[3,2-b:2′,3′-d]silole-5,5-diyl;4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl; benzo[b]thiophene;benzo[b]selenophene; benzooxazole; benzothiazole; and benzoselenazole;wherein all the aforementioned groups are unsubstituted, or substitutedwith one or more groups L, L is selected from P-Sp-, F, Cl, Br, I, —OH,—CN, —NO₂, —NCO, —NCS, —OCN, —SCN, —C(═O)NR⁰R⁰⁰, —C(═O)X⁰, —C(═O)R⁰,—NR⁰R⁰⁰, C(═O)OH, optionally substituted silyl or germyl, optionallysubstituted aryl or heteroaryl having 4 to 20 ring atoms, straightchain, branched or cyclic alkyl, alkoxy, oxaalkyl or thioalkyl with 1 to20 C atoms which is unsubstituted or substituted with one or more F orCl atoms or OH groups, and straight chain, branched or cyclic alkenyl,alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy oralkoxycarbonyloxy with 2 to 20 C atoms which is unsubstituted orsubstituted with one or more F or Cl atoms or OH groups, P is apolymerisable group, Sp is a spacer group or a single bond, X⁰ ishalogen, R⁰ and R⁰⁰ independently of each other denote H or alkyl with 1to 20 C-atoms, Y⁰ and Y⁰⁰ independently of each other denote H, F, Cl orCN, m is 1 or 2, n is 1 or
 2. 2. A compound according to claim 1,wherein R¹ and R² denote: —C≡C—R³, wherein R³ is an optionallysubstituted silyl or germyl group; or an aryl or heteroaryl group with 1to 20 ring atoms which is unsubstituted or substituted by one or moregroups L as defined in claim
 1. 3. A compound according to claim 2,wherein R³ is selected of formula II-AR′R″R′″  II wherein A is Si or Ge, and R′, R″, R′″ are identical ordifferent groups selected from the group consisting of H, astraight-chain, branched or cyclic alkyl or alkoxy group having 1 to 20C atoms, a straight-chain, branched or cyclic alkenyl group having 2 to20 C atoms, a straight-chain, branched or cyclic alkynyl group having 2to 20 C atoms, a straight-chain, branched or cyclic alkylcarbonyl grouphaving 2 to 20 C atoms, an aryl or heteroaryl group having 4 to 20 ringatoms, an arylalkyl or heteroarylalkyl group having 4 to 20 ring atoms,an aryloxy or heteroaryloxy group having 4 to 20 ring atoms, or anarylalkyloxy or heteroarylalkyloxy group having 4 to 20 ring atoms,wherein all the aforementioned groups are optionally substituted withone or more groups L′, and L′ has one of the meanings given for L inclaim 1, which is different from a silyl and germyl group.
 4. A compoundaccording to claim 3, wherein the compound is selected from thecompounds of the following formulae:

wherein R′, R″ and R′″ are as defined in claim
 3. 5. A formulationcomprising one or more compounds according to claim 1 and one or moreorganic solvents.
 6. An organic semiconducting formulation comprisingone or more compounds according to claim 1, one or more organic bindersor precursors thereof, wherein the organic binders have a permittivity ∈at 1,000 Hz of 3.3 or less, and optionally one or more solvents.
 7. Acharge transport, semiconducting, electrically conducting,photoconducting or light emitting material or component comprising oneor more compounds according to claim
 1. 8. An optical, electrooptical,electronic, electroluminescent or photoluminescent component or devicecomprising one or more compounds according to claim
 1. 9. A componentaccording to claim 7 which is a component selected from the groupconsisting of: organic field effect transistors (OFET), thin filmtransistors (TFT), integrated circuits (IC), logic circuits, capacitors,radio frequency identification (RFID) tags, devices or components,organic light emitting diodes (OLED), organic light emitting transistors(OLET), flat panel displays, backlights of displays, organicphotovoltaic devices (OPV), solar cells, laser diodes, photoconductors,photodetectors, electrophotographic devices, electrophotographicrecording devices, organic memory devices, sensor devices, chargeinjection layers, charge transport layers or interlayers in polymerlight emitting diodes (PLEDs), organic plasmon-emitting diodes (OPEDs),Schottky diodes, planarising layers, antistatic films, polymerelectrolyte membranes (PEM), conducting substrates, conducting patterns,electrode materials in batteries, alignment layers, biosensors,biochips, security markings, security devices, and components or devicesfor detecting and discriminating DNA sequences.
 10. A method ofpreparing a compound according to claim 1, comprising: a) halogenating2,3-Thiophenedicarboxaldehyde diacetal by lithiation with alkyllithium,LDA or another lithiation reagent, and then reacting with a halogenationagent including but not limited to N-chlorosuccinimide, carbontetrachloride, N-bromosuccinimide, carbon tetrabromide,N-iodosuccinimide, iodinechloride or elemental iodine, to obtain a5-halogenated 2,3-thiophenedi-carboxaldehyde diacetal, b) deprotectingthe halogenated diacetal under acidic conditions to the correspondingdialdehyde, which is then condensed with a cyclic 1,4-diketone to yielda quinone of the dihalogenated acenodithiophene, c) treating the quinoneof the dihalogenated acenodithiophene with silylethynyllithium, followedby a hydrolysis, to yield a dihalogenated diol intermediate, d)introducing heteroaryl groups in the dihalogenated diol intermediate bycross-coupling it with a corresponding heteroaryl boronic acid, boronicester, stannane, zinc halide or magnesium halide, in the presence of anickel or palladium complex as catalyst, to yield a heteroaryl extendeddiol, and e) aromatizing the heteroaryl extended diol using a reducingagent under acidic conditions to obtain a terminally substitutedheteroaryl acenodithiophene, or f) alternatively to steps b)-e),reacting the 5-halogenated 2,3-thiophenedicarbox-aldehyde diacetalobtained by step a) in a cross-coupling reaction with a correspondingheteroaryl boronic acid, boronic ester, stannane, zinc halide ormagnesium halide, in the presence of a nickel or palladium complex ascatalyst, deprotecting the resulting product and condensing it with acyclic 1,4-diketone as described in step b), followed by treatment withsilylethynyllithium and hydrolysis as described in step c), andaromatizing the resulting heteroaryl extended diol as described in stepe).
 11. A compound according to claim 3, wherein A is Si.
 12. A compoundaccording to claim 1, wherein X, in each occurrence, is S.
 13. Acompound according to claim 1, wherein n and m are both
 1. 14. Acompound according to claim 1, wherein Ar¹ and Ar² independently of eachother denote: furan; thiophene; selenophene; N-pyrrole; pyrimidine;thiazole; thiadiazole; oxazole; oxadiazole; selenazole; or a bi-, tri-or tetracyclic group containing one or more of the aforementioned ringsand optionally containing one or more benzene rings, wherein theindividual rings are connected by single bonds or fused with each other;and wherein all the aforementioned groups are unsubstituted, orsubstituted with one or more groups L.
 15. A compound according to claim1, wherein Ar¹ and Ar² independently of each other are selected from thefollowing moieties:

wherein X has one of the meanings of L in claim 1, o is 1, 2, 3 or 4,and the dashed line denotes the linkage to the adjacent ring in formulaI.